CRUSTACEAN LEG SEGMENTS — CARPENTIER & BARLET II3 



a segment of the leg more distal than the precoxopodite. What we 

 have found by carefully examining the exterior of the leg has been 

 confirmed — we think, in a conclusive manner — by the inspection of the 

 interior of the precoxopodite. Whether this segment has remained 

 free or has been imbedded in the thorax, it has displayed in both cases 

 features which correspond with those of an insect pleuron. It has 

 displayed the most typical relationships with the ventral endoskeleton 

 previously found in the Apterygota. Anaspides most resembles the 

 latter by the predominance of its subhypodermal endoskeleton, whereas 

 Penacus, by the development of its cuticular infoldings, is more like 

 a pterygote. 



The precoxopodite is thus morphologically equivalent to a uni- 

 laterally developed pleuron ; but is it the entire pleuron ? Most likely 

 not, for the precoxopodite does not directly articulate on the terguni 

 of the thoracic segment but on a "laterotergal" plate. This latero- 

 tergite bears posteriorly a process which the comparison with the in- 

 sects led us to call postpleural. The laterotergal plate seems to pertain 

 to a region homologous with the anapleuron of the Apterygota.^^ 

 On the proximal side we never saw it achieve a complete circle, but in 

 these arthropods, the anapleuron, in certain points, remains difficult 

 to analyze. 



According to these new data, what must we think of the "subcoxal 

 theory"? Of course it is beyond doubt that the originally basal ring 

 of the leg has secondarily been imbedded in the thoracic wall, but this 

 ring may very well have produced only a part of the pleuron. 



REFERENCES 



Barlet, J. 



1946. Remarques sur la musculature thoracique des Machilicies (Insectes 

 Thysanoures). Ann. Soc. Sci. Bruxelles, ser. 2, vol. 40, pp. 77-84- 



1951. Morphologic du thorax de Lepisma saccharina L. (Apterygote Thy- 



sanoure). Bull. Ann. Soc. Ent. Belgique, vol. 86, pp. 253-271. 



1952. Ressemblances entre le thorax de Nicolctia (Thysanoure Lepisma- 



tide) et celui d'autres Apterygotes. Bull. Inst. Roy. Sci. Nat. 

 Belgique, vol. 28, No. 54. 

 B6rnes, C. 



1903. Die Beingliederung der Arthropoden. Mitt. 3. Sitz.-Ber. Ges. naturf. 

 Freunde, Berlin, pp. 292-341. 



28 A priori, we can hardly accept the idea of the distinction of an "anapleuron" 

 and of a "catapleuron" (precoxopodite) starting with the Crustacea. Indeed in 

 the nauplius of various Crustacea, the segments of the sympod appear distinctly 

 only some time after the hatching (Heegaard, 1947) ; but for the phylogenist 

 what does this order mean according to which morphological details appear in 

 a larva such as a nauplius? 



