Fleury,

I know that :

We’ve been watching cells move (or not move) in embryos for a long, long time. There are no vortices of cell movement centering around the navel. Period.

Your model claim four counterrotating vortices centered around the navel. You failed to make your point by simply displaying them, since August 18, 2007 when I first tried to understand how those vortices could specify the limbs fields, as you also claim. That I know.

That’s a minor point concerning your model and your claims that :

The pattern of tetrapods exist in the platonician space of forms, just like the sphere. You can write its essence without evolutionnary arguments.

But it makes clear how you deal with reality, through the distorting lens of what boils down as an ideological a priori.

Your paper contain other examples of this particular behavior. Including inexistent data driven conclusions. Falsely reported results of colleagues. Imaginary correlations. Etc. How much do you think it takes for someone to decide to not take you seriously anymore? IMO you crossed the threshold by several orders of magnitude, several times.

It’s so easy to prove you wrong that I suspect the only support you can get is through ideologically related people (this includes Jean Staune, the “neolamarckian structuralist neo-creationist approaches from our local, Templeton Foundation supported, anti-Darwin bigot I was talking about”) or your Ecole Polytechnique centered network.
My guess: you will get more and more of the first type and less and less of the second one if you persist to follow your actual line of conduct.

You continuously and mostly inappropriately use the words “misconduct” and “defamatory“. I wonder how you qualify your way to deal with scientific critics by trying to silence them: by addressing their boss, or trying to shut down their blog (in my case), or threatening to sue them, instead of proving your point of view as one could expect from a scientist.

You sent, some time ago, an e-mail to my boss, hoping to silence me. Your message went down the drain (his computer’s trash actually) after he sent me a copy; which you didn’t judged convenient to do.
You have done the same for PZ Myers and people laugh at you and that’s the normal way things go, fortunately.
Maybe sometime you will learn that the hierarchical superiors may interfere with stuff on the web servers of the university, or letters with their lab’s address but not any private activity of their staff. You should have addressed your letter to the Scienceblogs editor, not the dean of the UMM.

In the past you have tried to distort what was said concerning your model and made me publish part of private messages to prove you wrong. You have also tried to rephrase what I have said, to make it sound favorable to your claims. You have done that again in your recent comment I’m answering here:

In addition, you aggregate with Mr Oldcola, who knows perfectly well that tehre are vortices.

.
I really don’t appreciate this and if you continue on the same line I’ll reconsider the proposal of Nerd of Redhead to contact your superiors at the MSC lab and university. Not to make it stop by asking them to use their authority, just to be sure that your cercle vertueux des laboratoires is aware of the kind of person you are and the way you act.

I’ll put my appreciation of your hypothesis and your ideological drives, clearly stated here, so you will be able in the future to link to it – using one of your favorite expressions:

bullshit; a big pile of stinking bullshit

and this applies particularly to your cteappv paper. The editorial board of EPJ should be ashamed to have accept it for publication.

Hope that this is clear enough. Grab the URL and use it as necessary.

Your comments always welcome will be published after copy was sent to Dr di Meglio.

Who moves whom during primitive streak formation in the chick embryo, Manli Chuai and Cornelis J. Weijer, HFSP J. 2009 April; 3(2): 71–76. Published online 2009 March 31. doi: 10.2976/1.3103933.

Those interested by following the discussion on this post two more pieces will be helpful : The ECM Moves during Primitive Streak Formation—Computation of ECM Versus Cellular Motion, Evan A Zamir, Brenda J Rongish, and Charles D Little, PLoS Biol. 2008 October; 6(10): 1–9, doi: 10.1371/journal.pbio.0060247 and of course An elasto-plastic model of avian gastrulation. Fleury V., Organogenesis. 2005 Jan;2(1):6-16 [epmag]. The later being the first publication of Fleury’s model.

I was awaiting Fleury’s reaction since April 2009 and it came just a few days ago. We had earlier a discussion about Zamir et al. paper which contradicts Flery’s model, which itself contains contradictory elements.

Let’s see figure 4 of epmag, depicting an epiblastic cell, “embedded between extracellular membranes, and crawling towards the posterior pole“.

The traction from both sides would be responsible, according to Fleury, for the production of “a crack in the extra cellular matrix“.

Earlier, in fig 3 of epmag, Fleury presented the deformation of “a solid [which] is pushed between plates” as being a parabolic (Poiseuille) deformation, with the flow being oriented towards the midline of the blastodisk.

In fact epiblastic cells are not embedded between extracellular membranes. I used this Fleury’s error to make clear during a few exchanges that he was attached to the idea of the Poiseuille deformation, thus a tensile deformation which can’t produce a crack at the midline, but rather ripples of the ECM. When I illustrated the fact that according to this point of view crack would be expected not at the midline of the blastodisc but at the rear of the cells I didn’t get any answer except that I had to think about it ; I don’t call that an answer.

When Zamir et al. paper was published, and because the authors pointed what I had illustrated with a lazy experiment almost a year earlier, that is that :

At the very least, our data suggest that somehow epiblastic cells pull the matrix toward the midline, rather than crawl across it.

and they also nicely illustrated once more that there are just two vortices at the epiblast’s level during early gastrulation, I added a few comments at an ongoing discussion with Fleury.

That didn’t lead us to resolve the contradiction or explain the “crack” which propagated till the cteappv (first occurrence p24,c2,§1).

The rather laconic and quite sibylline message I received isn’t of any help. Let’s go back to Chuai &Weijer’s paper.

It would be more appropriate to formulate the title as a question: “Who moves whom during primitive streak formation in the chick embryo?“

The conclusions of the paper leave the question open, after exposing what is known and what hypothesis may be tested to start getting answers and how to implement them:

These results [Zamir et al.] will need first of all confirmation by a series of independent experimental variations to test whether the labeled fibronectin molecules faithfully represent the dynamics of the matrix in vivo. If these results can be confirmed, then their thought provoking implications and some of the interpretations given by the Zamir et al. will need a lot more work to be substantiated and mechanistically understood. This will require the development and application of methods to identify cells that move actively and cells that are displaced passively, what forces are produced by cells in specific regions of the embryo, as well as methods to measure the mechanical characteristics of the extracellular matrix.

I “time is telling” something is that the model proposed by Fleury contains at least one major flaw (as two contradictory are proposed), maybe two as hypothetical solutions independent of Fleury’s model exist. And once more “time is telling” that there are two vortices on the epiblast, not four.

Recently, Fleury published on his website time-lapse animations supposed to show the two missing vortices, L2/R2. They time-travelled from early gastrulation to late neurulation. The latest animated gif is a detail without the somites but used to continuous and silent editing from Fleury according to remarks I kept a copy of the original. The description is:

Here especially, tracking of tissue flow by PIV technique, in vivo, in a chicken embryo (the blue cross is the last point, the green dots the subsequent positions superimposed on the final plate, with 5 minutes interval)

That’s a very special PIV technique. PIV stands for Particle Image Velocimetry and is usually performed seeding the observed flow with particles (not the case here) and using a LASER beam to illuminate a plane of the sample (not the case here) with a single camera (for 2D observations) or two cameras for stereoscopic 3D observations (not the case here, should be as the observed movements are complex due to neurulation). Anyway, the proposed cell trajectories have nothing to do with velocimetry!

On the other hand, you don’t set publicly available on the Net an image with EMBARGO on it, do you? Fleury do!

Reminder for Dr Fleury

Very nice from Dr Fleury to finally inform us of what L2/R2 could be. Never late to do well. The funny thing is that he commented here but haven’t send me a message about it! That’s weird. I’m asking for evidence concerning L2R2 since august 2007.

Let’s see what we have here anyway.

The first pair of vortices Fleury claims as R1L1 are shown by CuiC et al [Dev Biol. 2005 Aug 1;284(1):37-47. doi:10.1016/j.ydbio.2005.04.021, during stages ~1-3+.

For more than 2 years the presence of the R2L2 vortices was assumed to be visible during the same developmental period and modeled as the result of a single phenomenon.

The second pair of vortices Fleury claims as R2L2, presumably shown here, are situated between stages ~8-9+. They traveled in time!

Assuming that we have evidence for R2L2, the model presented by Fleury describing simultaneously the two pairs, R1L1 and R2L2, must be wrong and he should recall his paper (doi: 10.1051/epjap/2009033) and clarify this point (along with correcting everything else) before submitting it again.

Unfortunately, it seem's that the cell trajectories are manually spotted, the green color must not mislead anybody to confuse it as GFP expression, which is the case with Weijer's lab experiments. Manual spotting is not the best technique to follow a particular cell population during a process where everything is moving in 3D. Not even ink or membrane dyes were used!

The first gif file even as annotated by Fleury don't show any vortex.

The second gif file is even worse, it is obvious that the 2D depiction of the vortices is just false, sorry Dr Fleury, the cells/tissues movement is in 3D, you can't just get a projection in 2D and try to make it look as you would like it to be. This seems to be a recurrent problem. The animation starts when the 8th pair of somites is forming at stage 9+, always faraway in time.

Let me summarize Dr Fleury:

IF those are the R2L2, the vortices contributing to the formation of the hindlimbs THEN

the previous positioning at stages 1 through 3+ was false, as I have argued the last 2+ years

AND

the published models are false [cteappv (2009) & epmag (2005)]

AND that have nothing to do anymore with a 2D flow you claim to be at the origin of the tetrapods.

Now, we don’t really think we have evidence from a 2D manual projection of a 3D moving structure, in the absence of a tissular marker.

And I wonder what you will prefer, drop your model which assumes a (almost) 2D cellular layer and a hyperbolic flow forming simultaneously the four vortices, or try to get more consistent evidence (if any available).

So, Vincent Fleury always unable to deal with the scientific content of his publication seek other means to shut down critics.

It will be rather difficult.

In the mean time, an old rule I had to install for coffee&sci and dloale is back and this time it is applied in a wide scale. Vincent Fleury’s comments will not be accepted in any of my blogs except if there is a copy sent by e-mail previously, CCed to his boss; nowadays Jean-Marc di Meglio.

It is not that I don’t want his comments to appear here, I’ll be happy to see his replies and answers to comments and questions. Usually it’s fun stuff and it would be sad to miss it.
It’s just necessary to refrain his childish ways to behave and oblige him to focus on the subject rather than desperately trying to change it.

So Dr Fleury, your comments are to be moderated by your boss, not by me Whatever he accepts I’ll accept.
By the way, I wonder, is he’s aware of the content of your website?

First of all I would like to thank Mark, not for restoring my account, but, for the clarity of his replies, which is not often the case with people I had to communicate for other issues on various blogging platforms.

Anyway, I haven’t decided yet if I will continue with WordPress.com, confirm my migration back to Blogger, or have a WordPress blog hosted by some other provider than WordPress.com. I’ll need legal advice for the matter

The comment with Fleury’s IP and professional e-mail is hold for editing and it will certainly not contain the same info when it will come back. The info is available for who needs it via channels that don’t involve WordPress.com, but I think it’s not necessary anymore as Fleury’s movement tends to indicate that he really is the author of the weird comments posted at PZ’s and certainly the message PZ published.

I don’t understand why providing the IP and (already public) e-mail of someone could be threatening for his privacy. Wikipedia, including the French section, should be covered by complaints (maybe they are and they don’t give a shit about them).

Anyway, this is not the subject of this blog, just an accident, so I’ll resume with the critic of Fleury’s paper ASAP.

I opened The Mechanisms Underlying Primitive Streak Formation in the Chick Embryo, by Manli Chuai and Cornelis J. Weijer¹ for inspiration and of course Fleury’s webpage with his english short presentation.

Chuai & Weijer propose a simple model fitting their observations.

This is a rearrangement of elements from figure 1 (left panels) showing the transient vortices observed at the first stages of gastrulation at the epiblast level, bright field and epifluorescence, the marker being GFP expressed post-transfection and figure 3 (right panels) presenting a schema of their chemotactic model and the analogy with a hydrodynamic flow.

This is what Fleury describes as:

The usual picture of a development oriented in the antero-posterior direction is wrong. The recent dipolar description by Chuai, Weijer and co-workers is also wrong.

By saying so, he implies that the model don’t fit reality.
Maybe he failed to observe that the model proposed above include an area where V_x=V_y=0 at the center of Koller’s Sickle (KS)

How Fleury’s model fit reality? One may think that it must be better.

Let’s see:

The left panels as previously described, the right panel from Fleury’s model, tilted to align the axis to the one of the microscope images, the lower one being a superposition with the actual data. Pretty much the same frame of Weijer’s et al. time-lapse movie as the one Fleury used to position the missing vortices two years ago [fr but the images are international].

That would place the hindlimbs, according to Fleury’s, behind the KS!

A larger picture with the missing vortices annotated L2/R2:

not only “no L2/R2 – no hindlimbs” but also “if L2/R2, then hindlimbs behind the embryo!”

That doesn’t bother Fleury who prefers his model, coming out from the platonician space of forms, with the two invisibleimaginary vortices, instead of one quite realistic.

Make your mind. My preference goes to the one that stand reality check.

And if your name is Vincent Fleury and you are a theoretical physicist try to explain that.

Welcome guys.

Feel comfortable but be afraid, I’m the one manipulating the Master!
Using noodly appendages of course.

This one is from An Elasto-Plastic Model of Avian Gastrulation, Vincent Fleury, Organogenesis 2:1, 6-16, 2005.

[p13, col1, §4]

The extraordinary fact is that this equation is exactly the equation for two magnetic dipoles located at +a and -a near the caudal pole.⁸

Where 8 is given as: Bershadsky AD, Balaban NQ, Geiger B. Adhesion-dependent cell mechanosensitivity, Annual rev. oc Cell and Dev Biol 2003; 19:677-95.

OK, there is a small typo. But that’s not the problem.

Bershadsky et al. paper have just nothing to do with “two magnetic dipoles”! or any “caudal pole”. This is cell biology they are discussing there (abstract and full reference below).

Fast check:

• equation, absent,
• magnetic, absent,
• dipole, absent,
• caudal, absent,
• pole, absent

Slow check, I read the paper, nothing that could be confused with Fleury’s statement.

There are just 12 references in that paper, the first one I’m checking is wrong.

So,

The extraordinary fact is that this equation is exactly the equation for two magnetic dipoles located at +a and -a near the caudal pole.⁸

Either the reference is wrong or Fleury’s assertion. Or both.

Adhesion-Dependent Cell Mechanosensitivity

Alexander D. Bershadsky, Nathalie Q. Balaban, and Benjamin Geiger

Annual Review of Cell and Developmental Biology Vol. 19: 677-695 2003, doi:10.1146/annurev.cellbio.19.111301.153011

The conversion of physical signals, such as contractile forces or external mechanical perturbations, into chemical signaling events is a fundamental cellular process that occurs at cell–extracellular matrix contacts, known as focal adhesions. At these sites, transmembrane integrin receptors are associated via their cytoplasmic domains with the actin cytoskeleton. This interaction with actin is mediated by a submembrane plaque, consisting of numerous cytoskeletal and signaling molecules. Application of intrinsic or external forces to these structures dramatically affects their assembly and triggers adhesion-mediated signaling. In this review, we discuss the structure-function relationships of focal adhesions and the possible mode of action of the putative mechanosensor associated with them. We also discuss the general phenomenon of mechanosensitivity, and the approaches used to measure local forces at adhesion sites, the cytoskeleton-mediated regulation of local contractility, and the nature of the signaling networks that both affect contractility and are affected by it.

4.1 Tetrapod origin

If we turn to paleontology, we find a description of tetrapods appearance into three main steps. Appearance of chordates, segmentation of lateral fins, appearance of tetrapods.

That’s the shortest version one can get except “pouf they appeared”. Interesting nevertheless the second step, the “segmentation of lateral fins“. This is one of three hypothetical, not exclusive, working models. Not to be used as a granted fact (see below).

Good news, bad news.

Good news are that Fleury abandonned the idea it appeared in one of his conferences announcement, and promoted in fora, that the tetrapods may have appeared suddenly, with all there attributes, specifying suddenly as “in a single generation“.

But he still think that:

These early tetrapods have well formed complex limbs apparently almost “right away”.

Almost right away being an estimate of the time-lapse between Haikouichthys ercaicunensis, presenting a single median fin-fold and tail, to the tetrapodomorph Tiktaalik roseae; almost right-away corresponds to 100 millions years. At least we are not anymore at the “single generation“level.

Progressive modifications are problematic for a model which is based on a suddenly appearing bauplan.

4.2 About pentadactily

Well, certainly the bests Oops of this subsection. You can read about it here.

The idea to connect somites to fingers was not bad, but it doesn’t stand scrutiny, unless it’s Fleury who compares whatever to whatever (mixing mutants) forgetting or not caring to check the controls, and finally draws false conclusions.

This is not anymore about ignorance but rather about lousy methodology, not particularly connected to biology or physics. Of the general kind.

Reality check says that limb buds facing the same number of somites develop to pentadactylous limbs in wt embryos and nonadactylous embryos to double mutants.

The idea was interesting, but it doesn’t fit reality, so down the drain it goes (an old idea when it comes to Fleury’s theories).

And we find here also one of Fleury’s exact calculations, the “possible period doubling“, with 2*5={8,9,10}, a new kind of arithmetics.

And a second major Oops in the same subsection with the misrepresentation of fig. 21, wrong reference, wrong description.

Fleury wrote a few time ago [source: #63]:

To answer your comment [#50], yes, It was a physics paper, intended for physicists in a physics journal, so it makes little sense that somebody like Prof. Myers tries to review it, and then complain about the lengthy and tedious introduction. I find it weird that Prof. Myers should not be able to understand that a text is always intendend for a certain audience, it was not for people like him.

I wonder what that does mean. Because the expected audience was physicists that means that Fleury can serve them BS because they will not understand what they are served? And an embryologist’s opinion make little sense?
He is certainly right to think so, the referees didn’t understood what they were served after all. That doesn’t mean nobody will understand and explain them.

4.3 Fold extension

All fin-like appendages, be it anal, pelvic, pectoral or dorsal seem to be progressive extensions of superficial folds.

Not. Not folds, morphogenic fields (in the embryologist’s sense) which produce buds. There is probably shear stress acting as a positional cue integrated with other ones and participating in the morphogenetic events. But what specifies the morphogenetic field and produce the buds is cellular differentiation, that is differential genetic expression; that’s how folds are produced and what determines where and when they will be produced during the developmental process.

The AER is a typical example of an anatomic structure not being a fold, but an outgrowth of differentiated cells. But then Fleury may consider it as a fold, falsely believing (from a patently ignorant point of view) that in the normal case the AER is the junction of ectoderm and endoderm.

The discussion about the chorio-amniotic fold of the amniotes is interesting. Nothing to do with paleontology, no references concerning the timeline of its development to help connect the embryos curling with the fold‘s formation, an hypothesis out of thin air, expressed as an assertion (“The chorio-amniotic fold is analogous to a fin fold, except that the topology of the edge is a circle which closes up progressively like an iris, to form a hollow bag, and not a flat veil.“).
At least when it comes to the genetic components specifying its development he express his opinion as a belief (“I believe that a genetic analysis of the amniotic edge would give similar genetic inductions as a tail (see data base GEISHA [97]“). It could be, did he checked out the available data that could support this hypothesis? Or does he cite GEISHA just to bring false credibility to the hypothesis?

No mention of the neural fold, in plain sight (fig. 18), which doesn’t fit with the idea of proximo-distally extension.

Charles Darwin is wrongly cited here too. Maybe “scaffold” sounds better in Fleury’s ears, but it wasn’t used by Darwin.

This is also true of other edge-like organs, such as ears, nostrils or lips, which are well known to be observed in nature with almost “arbitrary” lengths, a word often used by Darwin.

Not very often, and never in association with “lenght”.

Citing Darwin doesn’t validate hypotheses, citing him (or anybody else) inappropriately, disrupts the argument.

So,

In the case of the pectoral and pelvic fins, they are believed to originate from a uniform fin present along the body; in the centre of this fin, an area was interrupted or somehow inhibited.

Again, no reference.

There is a quite interesting and relevant to the specific question paper (and for further discussion), by Yonei-Tamura et al.¹, addressing the presence of competent stripes for diverse positions of limbs/fins in gnathostome embryos, presenting three, non exclusive, work models:

Fig. 5. Model for the diversification of appendage morphology and its position in gnathostomes. Top: basic body plan for appendage formation with distinct features as a conserved developmental program; light blue indicates the lateral and dorsal competence for formation of limb/fin buds. Middle: appendages in early gnathostomes are formed by species-specific selection of limb/fin positions from the entire general competent region. Bottom: basic morphology and diversification of appendages in extant gnathostomes had evolutionally been established under the competence. Note that the animal retains competence in the dorsal and flank regions as shown in light orange.

One of them, middle/left of fig.5, fits with the hypothesis favored by Fleury. The authors compared msx1 expression in dogfish, skate and chicken, supporting the model by restricted gene expression domains between the three kinds of embryos (from fig. 2, panel Q¹ :

Schematic representation of msx1 expression in dogfish, skate, and chick embryos. Light and dark orange bars represent msx1 expression in the mesenchyme and ectoderm, respectively.

The skate embryo expressing msx1 in a way that gives an “8-shape” when observed from a dorsal or ventral point of view.

A very interesting information one can draw from this paper is that competence for limbs/fins is conserved to actual gnathostomes’ embryos and it comes in stripes rather then buds restricted at the limbs/fins morphogenic fields. And this information gathered by experimental data, confirming previous observations (including ref [65]).

Thus, the assertion

This is to say that it is not the regulatory loops of the genetic expressions which actually induced the splitting of the fin into limbs, but some “contraction”, which remains to be understood.

was obsolete before cteappv’s acceptation by EPJAP, the contraction being the one of of the limbs/fins morphogenic fields specifying genetic expression. One could have anticipated that this would be the case, from data available through the relevant scientific literature, Yonei-Tamura et al. paper being a systematic confirmation of previous results (which was necessary and is welcome), more than a revolutionary inout.

4.4 Limb extension

The fourth subsection starts quite badly.

Therefore, the situation in this field is not quite clear. It seems again that the same genes, already present prior to limb appearance, may serve to make a tail, a fin, or a limb, depending on where they are expressed, i.e., depending on the local geometrical context, and physical twists which occurred before genetic expression, in addition to chemical differences. This reminds of the fact that cnidarians and vertebrates have similar gene regulatory networks.

Hox genes where co-opted for specification of limbs, the central nervous system, the vertebral column, the gut, the genitals, the excretory apparatus and the hematopoietic system. They produce DNA binding proteins which act either as activators or repressors of transcription, depending of the differentiation state of the concerned cells and the integration of signaling events.
They indirectly (via the genes which expression they regulate) define geometrical context and in turn may be influenced by it as it specifies positional cues. Their role is evidenced by loss and gain of function experiments, limited by the pleiotropy of action of these genes (mutants development may be arrested before the onset to the developmental stage to be studied, e.g. limb development).

For the higher-then-the-cell level, genetic expression always precede geometrical variations, providing the molecular effectors and the energy necessary to produce them. Abrogating transcription (for tetrapods also mRNA maturation) and/or translation (i.e. gene expression) inevitably results in cell death; the single resulting mechanical effect observed being the cell’s collapse and desegregation.

That’s basic biology textbook knowledge and it’s really weird to have to introduce these basic notions while reviewing an already published paper. And they directly contradict the notion of geometrical context and pysical twists occurring before genetic expression.

And facts concerning the similarity of GRNs between cnidarians and vertebrates should be adequately revised.

Later during evolution limbs disappeared from some tetrapod lineages which became aped, such as snakes.

Adult tetrapods may be limb-less because limbs don’t develop. The natural pattern of tetrapods is just tetrapod. If some species doesn’t conform with it’s just not a tetrapod. Easy to grasp, even for physicists. The adult of some species are limbless.
Fleury rightly concludes that for a species to be considered as tetrapod it must be a tetrapod! Puzzling, right?

The fact that hindlimbs form first [...]

is just one (more?) of the authors fantasies and certainly not a general fact, the forelimb-hindlimb developmental timing changes across tetrapod phylogeny. BIBO rule applies here, also.

4.5 Limb flexion

Articulations of the zygo- to auto-pode and stylo- to zygo-pode have being demonstrated to be sensible in respect to their orientation to ectopic gene expression which is able to change them.

This is a huge problem for the model Fleury propose, and his effort to minimize experimental results is ridiculous, and some ensuing statements are quite curious:

If this experiment would be confirmed, it would be an uncommon case of a chirality, directly induced by a scalar non-chiral field. This would suggest that Tbx5 codes for a chiral molecule.

If one needed an additional proof that the author really don’t understand what he is talking about, he got it. I really don’t find what to say about the degree of ignorance showcased here, except once more suggest that Fleury should RTFM and avoid talking about transcriptions factors before doing so.

Concerning limb flexion and Fleury’s model:

1. Limbs grow in a reverse way than the model predicts,
2. but this isn’t really important as the limbs flexion is represented by the model falsely, the third dimension lacking, and no mechanism is proposed for the instruction of the direction of flexion of the limbs, between the assumed vortices and the orthogonally growing limb.

This is the second predicted feature of the model, after limb positioning and is patently flawed.

Last in this subsection, one more display of Fleury’s poor understanding of biological literature, the way he reports the work of Liao & Collins, unable to make the distinction between an intoxication (reality) and a mutation (Fleury’s point of view) and correctly report on the “duplication of the entire body axis” which the authors report as lethal beyond gestation day 9 (reality) and are here considered necessary for the apparition of additional limbs (Fleury’s point of view).

1. Competent stripes for diverse positions of limbs/fins in gnathostome embryos, Sayuri Yonei-Tamura, Gembu Abe, Yoshio Tanaka, Hiromasa Anno, Miyuki Noro, Hiroyuki Ide, Hideaki Aono, Ritsu Kuraishi, Noriko Osumi, Shigeru Kuratani, and Koji Tamura, Evolution & Development 10:6, 737–745 (2008)

My very first objection concerning Fleury’s model¹ was that he described the epiblast cells as contained between two extracellular membranes. When I pointed that his only response was that if there is a single basal membrane that doesn’t affect his model, the flow would be just faster. From that point on you can’t trust the guy with any description.

Assuming, once more for argument’s sake, that there would be four vortices on the center of which the limb fields develop, could that explain, as Fleury presents the flexion of the limbs ? I asked one question which is still unanswered by Fleury more than ten days later.

His description doesn’t fit with his description. We have here an inner contradiction of his model that gone under his radar. The limbs growth doesn’t follow the vortices flow. That’s sad, but it’s not the worse part of it. Let’s add an new-dimension.

Fleury so much like to consider embryos as rather flat entities that he forgotten the third dimension. Not completely. In Fig 37, panel a, he present us a stage 4 embryo of Eleutherodactylus coqui, with a personal annotation showing the vortices:

On the left the original from Richardson MK et al.² paper, on the right Fleury’s interpretation of the positioning of the vortices. As we have see, when it come to limbs flexion, this third dimension vanish and the schemas of fig. 38 are flat.

The growth of the limb bud is orthogonal to the plane of the vortex, let’s represent it as below:

the vortex in yellow, rotating clockwise and the bud growing upwards.

When it come to define the flexion at the junction between the stylo- and zeugo-pode what would be the mechanical mechanism that would instruct a particular direction for the bending ? I represented below the development of the limb with the stylopode in blue, the zeugopode in green and the articulation (elbow or knee) as a pale blue sphere. (four directions in color, plus four as gray ghosts, and infinity of case not represented)

None presented, despite the role Fleury attribute to limbs flexion.

Let’s see what that would give us if we try to map it to the four vortices model:

(here the vortices are in red to improve visibility) The AnteroPosterior and DorsoVentral directions are annotated, along with the cartesian (orthogonal) coordinates system. The latter is just represented to show how much inappropriate it may be to confound the embryos axes to it.

There is no relation between the vortices and the limbs flexion, limbs proximodistal axes being parallel between them and to the Z axis.
The real stuff in almost the same orientation as the above schema:

with the direction of growth of the limbs in white (insert, original).

Both papers freely available
1. An Elasto-Plastic Model of Avian Gastrulation, Vincent Fleury, Organogenesis 2:1, 6-16, 2005
2. Limb development and evolution: a frog embryo with no apical ectodermal ridge (AER), Richardson MK, Carl TF, Hanken J, Elinson RP, Cope C, Bagley P. J Anat. 1998 Apr;192 ( Pt 3):379-90, doi: 10.1046/j.1469-7580.1998.19230379.x.