1 1 6 whitman: [Vol. I. 



that his conclusions had been anticipated, and turns at once to the 

 more agreeable task of contradicting Hoffmann's account. His 

 own observations are then detailed as follows. Beginning with an 

 embryo in which the somites are already distinctly marked from 

 end to end, and the nephridia differentiated, he says: "II se 

 montre sur toute la surface externe du vitellus une couche pro- 

 toplasmique granuleuse (^en) avec des noyaux ovoides et arron- 

 dis ; cette couche, developpee aux depens des elements cellulaires 

 de I'entoderme primitif, se transforme ensuite en epithelium intes- 

 tinal. Hoffmann a observe aussi une semblable couche proto- 

 plasmique avec des noyaux ovoides, mais il I'a consideree comme 

 un produit du mesoderme. Cependant j'ai vu plusieurs fois, 

 sur des coupes tres minces et parfaitement colorees, que cette 

 couche est delimitee d'une maniere tres nette de la couche de 

 cellules plates du feuillet visceral du mesoderme, tandis que du 

 c6te interne la couche protoplasmique passe directement dans 

 le vitellus ; ainsi I'origine entodermique de cette couche ne pent 

 6tre soumise a aucun doute " (p. 9). 



This is all that Nusbaum has to tell us about the origin and 

 history of the entoplasts. The whole alimentary tract is lined 

 with cells of the same origin. "Ainsi le resultat final est que 

 I'epithelium (plat) tapissant la cavite de la trompe represente 

 un produit entodermique. Tout I'intestin post^rieur represente 

 de m^me un produit entodermique" (p. 11). The sequel will 

 show that Nusbaum has added very little to what was already 

 known on this subject. 



Bergh (No. 9, pp. 259-260) confirms my statements in regard 

 to the existence of peripheral nuclei in the three entoblasts, but 

 rejects the hypothesis that they represent the entoderm, as in- 

 compatible with what is known about the origin of this layer in 

 the Gnathobdellidae. 



Nephelis. — According to the observations of Kowalevsky 

 (No. 10, p. 3), Biitschli (No. 11, ), and Bergh (No. 9, p. 259), 

 the entoderm in Nephelis arises immediately after the eight-cell 



(9.) Bergh, R. S. Die Metamorphose von Aulastoma gulo. Arbeiten a. d. 

 zool.-zoot. Institut in Wurzburg. VII., H. 3, p. 231. 1885. 



(10.) Kowalevsky, A. Embryologische Studien an Wiirmern unci Arthro- 

 poden. Mem. de r Acad. Imp. de Sc. St. Petersburg. XVI., No. 12. 1871. 



(11.) BiJTSCHLi, O. Entwiclilungsgeschichtliche Beitrage. Zeitschr. f. wiss. 

 Zool. XXIX., p. 239. 1S77. 



