658 General Notes. 
this difference, there is an irregular and abnormal mode of devel- 
opment which does not present it at all, and which, under the con- 
dition of the primitive relations of the calyx and of the peduncle, 
presents the same disposition as in all other Echinoderms; that is 
to say, that in which the calyx is inserted at one side. We are 
therefore led to conclude that the difference here noted is not a 
fundamental one, but that it constitutes a simple alteration of the 
primitive plan common to all other Echinoderms, resulting from 
fixation and which disappeared immediately after that fixation 
ceased to occur. 
Second difference. — In the ordinary Echinoderm larva (Asterias, 
Echinus), the two peritoneal vesicles maintain their primitive situa- 
tions, the one at the right and the other at the left, the dorsal face 
(aboral) of the future Echinoderm being formed at the expense 
of the portion of the larva which answers to the left peritoneal 
vesicle. Asa result there is a singular discordance between the 
two faces of the adult and the two faces of the larva, which has 
been noted by numerous observers, and which consists in this, that 
the right side of the larva becomes the dorsal face, and the left side 
of the larva the ventral face of the adult, so that the now outline 
Echinoderm is found to be placed in a transverse and a symmetri- 
cal position in relation to the preoral lobe of the larva. In Coma- 
tula, we have seen, on the contrary, that the ventral and dorsal 
faces of the larva correspond respectively to the ventral and dorsal 
faces of the adult in such a manner that the outlined adult (or 
calyx, in other words), instead of being placed transversely to the 
peduncle, occupies a symmetrical and regular position in relation 
to the latter. ; 
e have seen, however, that there is not such a discordance 
between the positions of the dorsal and ventral aspects of the larva 
and adult Comatula, and that the two peritoneal sacs here, instead 
of maintaining their primitive position as in other Echinoderms at 
the right and left of the embryo, set out on the fifth day, in Coma- 
tula, to change their positions, the right sac becoming dorsal, an 
the left one ventral. Now, if we admit that the formation of the 
dorsal and ventral faces are subordinated to the position of or 
peritoneal sacs, we arrive at the conclusion that the displacement 0 
the peritoneal sacs as described above, is a sufficient explanation 
of the differences noted at the outset. : 
which 
Barrois, 25 
compared with those of Busch, Thompson, Metschnikoff, Gotte and 
sible of 
