ANATOMY AND PHYSIOLOGY, EMBRYOLOGY. 
Moll 7 
produced by acids. The same also in Atti Univ. Genov, iii. ; and an 
abstract, by A. IssEL, containing a part of the coloured illustrations, in 
“Rivistamaritima,” Sept. 1876. 
Embryology. 
A short recapitulation of our knowledge concerning the development 
of the Mollusca is given by W. K. Brooks, P. Bost. Soc. xviii. pp. 
225-232 ; he thinks that the Lamellihranchia deviate more from the 
typical larval form than the Gastropoda, although the latter are more 
highly developed, and that for making out the phylogeny of the Mol- 
lusca we must compare the larval form provided with a velum {veliger) 
with other classes of the animal kingdom ; he endeavours to show a 
homology between this larval form and the Polyzoa. 
E. Ray Lankester has published in full his observations and views on 
the development of Pisidium, Aplysia, Pleurohranchidium, Tergipes, 
Polycera, Neritina, Limax, and Limnceus in Phil. Tr. 1875, 48 pp., 12 pis. 
(see Zool. Rec. xi. p. 117, and xii. p. 138). 
Pol’s observations on the embryology of the Pteropods [see Zool. Rec. 
xii. p. 137] are fully published in Arch. Z. exper. 1875. 
Bobretzky, from observations made on Nassa, Fusus, Natica, &c., by 
cutting sections after hardening the embryo in chromic acid, comes to 
the same conclusions as H. Pol [Zool. Rec. xii. p. 137], in opposition to 
E. Ray Lankester, that the opening formed by the invagination of the 
primitive embryonal layers becomes afterwards the mouth of the 
animal ; Arch. mikr. Anat. xii. pp. 95-169. O. Butschli, however, has 
observed in Paludina vivipara, that this opening becomes the vent, as 
E. Ray Lankester has already stated, and that the mouth is formed at 
the same time as the so-called shell- gland by invagination of the ectoderm. 
Z. wiss. Zool. xxvii. pp. 518-521 ; and Arch. mikr. Anat. xii. pp. 95-169. 
The first stages of development in the genus Unio have been again 
observed by 0. Rabl ; he comes to conclusions which somewhat differ 
from those given by W. Plemming [see Zool. Rec. xii. p. 139], as he 
describes a true invagination, by which the primary intestinal tube is 
formed ; the development of this tube is soon stopped, and it becomes 
quite rudimentary in the parasitical stage, when the young animal is 
fixed to the skin of fishes ; the long byssal filament and the strong 
marginal teeth in the shell of the young animal are likewise adaptations 
to this parasitical life. The author finds his observations fully agreeing 
with HiickePs theory of the germinal layers (Keimblatter) and expa- 
tiates on the homologies of the individual organs with those of other 
Mollusca and Molluscoidea, Jen. Z. Nat. x. 86 pp. and 3 pis. 
W. Plemming discusses some statements made by E. Ray Lankester, 
Rabl, and Hackel, concerning the embryology oE the Unionidcc, and 
compares them with his own results, declining in most cases a final 
decision. Z. wiss. Zool. xxvi. pp. 355-360. 
H. V. Ihering makes some observations on the first development of 
Cyclas \^Sph(crium~\, denying the formation of a Gastrula-form in it, and 
