ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 303 



There are two types, papilla-like and pocket-like, with transitions. The 

 pocket type is often changed in form by the contraction of the skin, and 

 may be protruded. 



The organ consists of a layer of thickened epithelium with nerve- 

 endings. The olfactory epithelium consists of ciliated cells and sensory 

 cells, the latter being deeply situated, probably amoeboid, with a peculiar 

 slightly pigmented body inside and a rounded or rod-like terminal 

 process. 



The " olfactory nerve " does not arise from the ganglion pedunculi 

 ("olfactory ganglion"). Its fibres run in close association with the 

 optic nerve, and are probably not exclusively of cerebral origin. The 

 " olfactory organ " of Dibranchiata is in its innervation homologous with 

 the rhinophores of Nautilus, but not with the osphradia of other molluscs. 

 It is probably an organ of chemical sense for testing the water. 



y. Gastropoda. 



Abnormalities in Genital Ducts of Helix pomatia.* — Gustav 

 Poluszynski describes some variations, e.g. in the presence of a short 

 diverticulum on the duct of the receptacnlum, a trace of its connection 

 with the oviduct during development. In five cases the duct of the 

 receptaculum divided into two for a short distance and then became one 

 again. The duct of the receptaculum is phylogenetically the youngest 

 part, and it shows considerable variability, notably of a reversionary sort. 



Spermatogenesis in Helix. f — Max Kleinert gives a detailed account 

 of the stages of spermatogenesis in Helix (Tac/tea) nemoralis and hor- 

 tensis. The spermatogonia have forty-eight chromosomes, among which 

 are two particularly large and bent or horse-shoe shaped. The two large 

 chromosomes divide longitudinally ; in the small chromosomes the direc- 

 tion of the division was not clear. Full particulars are given of the 

 reduction to twenty-four chromosomes, of the idiozome or " Nebenkern," 

 and of the differentiation of the spermatozoon. There is in the sperma- 

 togenesis no difference between the 5 -banded and 3-banded forms of 

 Helix nemoralis, or between the unhanded and banded forms of Helix 

 hortensis. 



Noises made by Snail on Window-pane. % — Fred Vies discusses this 

 problem, in regard to which there is considerable difference of opinion. 

 His observations lead him to conclude that the grating noise is due to 

 the shell, not to the radula, and that there is another rarer noise of un- 

 known origin, like that made by the bursting of a large bubble on the 

 surface of water. 



S. Lamellibranchiata. 



Commensal Lamellibranchs.§ — Paul Pelseneer discusses Montacuta 

 found on Echinocardiurn and Spatangus, Entovalva Voeltzkow in the 

 gullet of Synaptids, Scioberetia Bernard on a sea-urchin (Tripylus), and 



* Bull. Internat. Acad. Sci. Cracovie, 1910, pp. 17-20. 



t Jen. Zeitschr. f. Natur., xlv. (1909) pp. 445-9S (4 pis. and 22 figs.). 



% Bull. Soc. Zool. France, xxxiv. (1910) pp. 251-4. 



§ Bull. Acad. Roy. Belg.,Classe des Sciences, 1909, No. 12, pp. 1144-50. 



