18 Moll. 
MOLLUSCA. 
other worm-shaped ; the former only is essential for the fecundation of 
the egg, the other is the result of a less numerous partition of cells, and 
is to be regarded as homologous to the eggs in the female individual* 
M. v. Brunn, Zool. Anz. 1883, pp. 89-92. 
8. Embryology. 
The embryonal development of Aplysia limacina (L.) is described by 
F. Blochmann, Z. wiss. Zool. xxxviii. pp. 392-410, pis. xx. & xxi. The 
most interesting observation on which he dwells is that the blastopore> 
being a long cleft, gives origin to the mouth as well as to the anal open- 
ing ; this will reconcile the otherwise contradictory statements made by 
other authors, that the blastopore gives in one animal origin to the mouth, 
and in another to the anal opening. Abstract in JB. mal. Ges. xi. [1884] 
p. 292. 
C. Rabl has observed in Paludina vivipara that the gastrula mouth 
or blastopore closes completely, and is not connected in any way with the 
anus, which makes its appearance somewhat after its closure, and that the 
permanent mouth appears still later on the same spot. SB. Ak. Wien, 
lxxxvii. Abth. 3, pp. 45-60 ; preliminary note in Anz. Ak. Wien, 
January, 1883, p. 13 ; abstract in Ann. N. H. (5) xi. p. 222, and J. R. 
Micr. Soc. (2) iii. p. 192. 
Abstract of P. B. Sarasin’s paper on the development of Bithynia 
tentaculata in J. R. Micr. Soc. (2) iii. pp. 36-38, and JB. mal. Ges. xi. 
[1884] pp. 294-298. 
Observations on the structure of the velum, the origin of the upper 
oesophageal ganglion, the structure of the primitive kidneys, and the de- 
velopment of the persistent kidneys, in Bithynia tentaculata ; C. Rabl, 
SB. Ak. Wien, lxxxvii. Abth. 3, pp. 50-55, with a plate ; abstract in 
Anz. Ak. Wien, January, 1883, p. 13, and J. R. Micr. Soc. (2) iii. p. 193. 
On the first stages of development in Aplysia ; L. DE Manfredi, Atti 
Acc. Nap. ix., App. No. 3 [not seen by Recorder]. 
A. Kowalewsky describes the first stages of development in Chiton 
polii (Phil.) and Dentalium. He comes to no general conclusions upon 
the former, but observes as to the latter that the segmentation is very 
like that of the Bivalves, the invagination resembling that of Chiton ; 
the shell-gland makes its appearance very early, the middle part of the 
intestine is formed by invagination, and the cerebral and pedal ganglions 
originate from the ectoderm, the former by invagination of the sincipital 
plate ; the larva of Dentalium externally somewhat resembles that of 
the Annelids, but differs internally wholly from them. Ann. Mus. Mar- 
seille, i. Nos. 5 & 7, 92 pp., 16 pis. 
H. Rouzaud publishes some observations on the development of the 
generative organs in the Pulmonata ; C.R. xcvi. pp. 273-276; abstract 
in J. R. Micr. Soc. (2) iii. p. 192. 
J. Leidy states that the weight of the embryos in the gills of a single 
Anodonta fluviatilis was 56*66, and in another specimen 40*43 grammes, 
whereas the weight of the animal without embryos was 78*78 and 73*45 
grammes. P. Ac. Philad. 1883, pp. 44 & 45 ; also Science, i. p. 150. 
