16 Moll 
MOLLUSCA. 
nation of the ectoderm in the terrestrial Puhnonata, and in a thickened 
spot of the mesoderm in the aquatic ; but the mesoderm itself originates 
in the ectoderm. The origin of the pulmonary cavity is the same in both 
terrestrial and aquatic species, and is independent of the kidney (opposed 
to the statement of Ihering). There is a pair of renal organs in the 
larva, which disappear afterwards; the later permanent kidney is 
developed only on one side of the body, and wanting or rudimentary on 
the other. The asymmetry in the structure of the body begins very 
early in the embryo, soon after the segmentation of the yelk, and it 
cannot be stated that it is caused by any distinct organ. The contractile 
sinus at the end of the foot in the larva of the terrestrial Pulmonata is 
formed by a part of the wall of the body, and, on account of its situa- 
tion, is not identical with the contractile parts in the foot of the aquatic 
Pulmonata. The author comes to the conclusion that the embryonal 
development of the Mollusca agrees remarkably with that of the Vermes^ 
Polyzoa, Brachiopoda, Echinodermata^ and even Ccelenterata ; whereas 
the Arthropoda and the Chordonice {Vertehrata and Tunicata') exhibit two 
other types of development. Arch. Z. exp6r. viii. pp. 103-232, pis. ix.- 
xviii. ; abstract in J, R. Micr. Soc. iii. pp. 414 & G05. 
C. Rabl maintains his views and statements as to the first develop- 
ment of Planorh'iH against Fol’s criticism, and adds only that what had 
been described as “ pedicle of invagination” by Lankester is not a residue 
of the process of invagination, but a distinct development 'of a part of 
the small-sized endodermic cells, and that the number of cells is not 24, 
but 25, at the time when the separation in distinct germinal layers is 
beginning. Morph. JB. vi. pp. 571-580, pi. xxix. ; abstract in J. R. Micr. 
Soc. (2) i. p. 25. 
W. Wolfson’s paper on the embryology of LymncBus \_Limnoia'\ 
stagnalis, written in Russian, in Sap. Acad, xxxvi. [1879] No. 2, is 
abstracted by the author in German ; M^l. Biol. x. pp. 351-377. The 
author describes the segmentation of the egg, and comes to the result 
that the intestine is originally closed at both ends, and that the vent is 
subsequently formed by invagination. Abstract in J. R. Micr. Soc. iii. 
p, 415. 
W. H. Brooks gives a preliminary statement of the leading points in 
the development of the Pulmonates and of the Oyster, from original 
observations, with the following conclusions: — “ The Pulmonate and the 
Lamellibranch resemble each other in having the blastopore converted 
into the shell area, and the mouth formed nearly opposite by an invagi- 
nation of the ectoderm. In both groups the anus is distinct from the 
blastopore, and is formed after, the obliteration of the latter and the 
formation of the mouth, but the invagination neck of the Pulmonate 
migrates from its primitive position to the new anus, and becomes con- 
verted into the intestine, while the intestine of the oyster appears to 
have no relation whatever with the invagination neck.” P. Bost. Soc. 
XX. pp. 325-329 ; abstract in J. R. Micr. Soc. iii. p. 763. 
S. Trinchese describes the first changes in the egg before and soon 
after fecundation, in two Nudibranchiata, Amphorina ccerulea (Mont.) 
and Ercolania aiottii (Trinch.), with special regard to the directory 
