ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
465 
that the animals glide along the surface. In capturing small leaves, &c., 
the foot is often very dexterously used. Besides aquatic plants and 
small animals, the snails sometimes find larger booty, e. g. the larvm of 
Mayflies. 
Nervous System of Nerita polita.* — M. L. Boutan finds that Nerila 
polita (and Navicella porcellana ) present a crossing of the commissures, 
such as is seen in other Aspidobranchs. The right branch is represented 
by an extremely delicate nerve. The gill is innervated both by the first 
right ganglion and the first left ganglion of the asymmetrical centre. 
The nerve-cords in the foot are solely formed by the pedal ganglia, 
which have the otocysts on their hinder part. The inferior lobe of the 
mantle is directly innervated by the first two ganglia of the asymme- 
trical centre. M. Boutan is led, therefore, to conclude that the Neritidse 
are chiastoneurous and not orthoneurous, as stated by M. Bouvier. 
M. E. L. Bouvier,| referring to M. Boutan’s communication, states 
that he has discovered in Nerita plexa a supra-intestinal nerve-branch 
which had before escaped him. Having examined several allied forms 
he is now inclined to think that all these orthoneuroid Prosobranchs 
are really chiastoneurous. It is clear that the Neritidae and Helicinidae 
are allied to the other diotocard Prosobranchs, and the idea that there 
are two divergent series of Prosobranchs must be altogether given up. 
The facts adduced by the author seem to destroy the chief argument of 
those who do not consider that the crossing of the nervous system is the 
consequence of the displacement of the anus. 
Anatomy of West Indian Helices.! — Mr. H. A. Pilsby finds that 
the genital system of Caracolus is simple, while that of Hemitrochus is 
complicated by a large dart-sac, and several unequal accessory glands ; 
there is a long flagellum of the “ whiplash ” type, while that of Caracolus 
is short. 
Two rare British Nudibranchs.§ — Mr. F. W. Gamble gives fresh 
descriptions of Lomanotus genei , and Eancockia eudactylota ; a single 
specimen of each species was obtained by him in Plymouth Sound. 
Cnidocysts were carefully looked for in the former, but were not 
detected. Govia viridis Trinchese is a synonym of the latter. The 
dorsal papillae of Lomanotus respond to stimuli, but those of Eancockia 
do not. 
Zoological Position of Solenoconcha.||— Dr. L. Plate has investi- 
gated the zoological position of Dentalium and its allies ; and concludes 
that the eight following points are indications of a closer affinity to the 
Gastropoda than to the Lamellibranchiata : the unpaired shell, the 
radula, the jaws, the tentacles, the retractor-muscles which appear to be 
homologous with the columellar, the presence of pleural ganglia, which 
are rarely seen in Lamellibranchs, the extreme development of the 
buccal ganglia, and the possession of oesophageal glands which seem to 
correspond to the salivary glands of Gastropods. Grobben’s view that 
* Comptes Kendus, cxiv. (1892) pp. 1133-5. f Tom. cit., pp. 1281-3. 
X Proc. Acad. Nat. Sci. Philaa., 1892, pp. 128-9 (1 pi.). 
§ Ann. and Mag. Nat. Hist., ix. (1892) pp. 378-85 (1 pi.). 
|| Verhandl. Deutsch. Zool. Ges., 1891, p. 60. See Amer. Nat., xxvi. (1892) 
pp. 347-8. 
1892. 9 K 
