ANATOMY, PTIYSIOLOGY, AND EMBRYOLOGY. 
117 
Anatomy, Physiology, and Embryology. 
H. Grenacher maintains that what is called the foot in the MoU 
lusca, consists morphologically of two essentially different parts — the 
propodhim, which is single from the beginning, and the epipodiuniy which 
is originally formed by a pair of prominences. The epipodium is trans- 
formed in the Cephalopods to the funnel, in the Pteropods to the 
lateral fins. No trace of propodium is to be found in the Cephalopods; 
their arms probably correspond to the velum of other Mollusca. Z. wiss. 
Zool. xxiv. pp. 507-577. 
The peculiar nervous organ detected by Lacazo-Duthiors in the 
Limn<v,i(l(G [see Zool. Hoc. ix. p. 101] is regarded as olfactory l)y Von 
Ihering, from its analogy with a similar one in the Pteropods and 
Heteropods. JB. mal. Ges. i. p. 166. 
On “ fungoid ” growth in the shells of Mollusks. M. Stirrup, P. Soc. 
Manch. xi. (1872) p. 137. 
Copper in the blood of Helix nemoralis and pomatia. Siegert, Ber. 
Ges. Chemnitz, iv. (1873) p. 69. 
Decrease of weight in Helix pomatia during winter; Sievers, SB. 
Ges. Dorp. iii. p. 299. 
Notes on spermatozoids of Helix j^omatia^ Clausilia hiplicata, and 
Cyclas cornea ; La Valette, Arch. mikr. Anat. x. pp. 495-504, pi. xxxv. 
The formation of the egg in the Mollusca is reviewed, with careful 
reference to the literature of the subject, by H. Ludwig, Arb. Inst. 
Wiirzb. parts v. & vi. pp 369-379 (Verb. Ges. Wiirzb. 2nd ser. vii. pp. 
115-125). The author comes to the conclusions that the egg is a simple 
cell, representing a transformed epithelial cell, and that it is surrounded in 
the Hivalvia, Puhnonata, and Cephalopoda by a primary cover, which is 
to be called vitelline membrane (Dotterhaut), and further in all Mollusca 
by a secondary soft cover, secreted in the Gastropoda and Cephalopoda 
by peculiar glands or by the walls of the oviduct, whereas in the Bivalvia 
its origin is not yet exactly known. 
E. Ray Lankester, from his observations on the development of various 
genera, concludes that in all young Mollusks there is a peculiar secreting 
organ, formed by invagination of the dorsal surface, and to be called 
shell- gland in some genera it secretes a chitinous matter, which even- 
tually disappears, in others it gives origin to a true internal shell, as in 
Sepia and Limax. The embryo of the Mollusca ordinarily undergoes 
three stages:— the first, that of a Gastrula\ the second, when girdled 
with a row of cilia, is called Trochospheera ; and the third, distinguished 
by the development of the velum, Veliger. Q. J. Micr. Sci. (2) xiv. 
pp. 365-391, pis. xvi. & xvii. The author also states that ho has observed 
the typical Gastrula-^i?igQ in Pectiuibranchiate Gastropods {Paludina)^ 
Nudibranchs [Tergipes^ Polycera), Pulmonates {Limax, Limncea), and 
Bivalves {Pisidium). Ann. N. H. (4) xiv. pp. 81-86 & 458-460 ; also in 
P. R. Soc. xxii. pp. 232-238. 
On development of Cephalopods and Pteropods, Limncca, Calyptra’a, 
and Anodonta, see infra. 
