208 SUMMAEY OF CURBENT RESEARCHES RELATING TO 



apparently no relations to the byssus, it is still more different from 

 the second valve of a Lamellibrancli shell. 



Anatomy of the Stylommatophora.* — A. Nalepa has been chiefly 

 engaged with Zonites algirus, but has also investigated Limax 

 cinereoniger, and Helix pomatia. The large mucous glands which are 

 so often enormously developed in the integument of land pulmonates 

 are proportionately only feebly developed in, and are indeed absent 

 from parts of the skin of Zonites. Transverse sections of the edge of 

 the mantle of Helix show conclusively that the tunica propria of the 

 mucous glands is continued between the epithelial cells. Zonites has 

 no winter operculum, and the absence of this may explain the rare 

 presence of calcareous glands. The author thinks that Simroth's 

 criticism of the supposed olfactory function of the foot-gland is 

 justified by its structure, for maceration shows that it is an agglomera- 

 tion of unicellular glands. As to the nervous system of the foot, it is 

 to be noted that there are not two primary trunks, inasmuch as the 

 diameter of what have been so regarded is often surpassed by that of 

 their lateral branches. 



The different reports that have been made on the distribution of a 

 ciliated epithelium in the enteric canal, are partly, at any rate, to be 

 explained by such facts as that the whole stomach is ciliated in very 

 young Helices, while, in the adult, wide tracts are devoid of cilia. 

 The salivary glands of Helix are loose, but in Limax and Zonites 

 compact masses, which in the former lie like a saddle on the short 

 oesophagus, and in the latter form a pretty broad closed ring ; they 

 are made up of a number of unicellular glands, and each cell is sur- 

 rounded by a membrane of connective tissue, which, at its side, is 

 continued into a narrow and generally very long efferent duct. The 

 cells have either finely granular or hyaline contents, and have a 

 different reaction with osmic acid. Each salivary gland receives a 

 strong nerve from the buccal ganglion, and there is a general 

 distribution of the large ganglionic cells, which are characteristic of 

 the sympathetic system. 



The arteries are continued into capillaries with definite walls, 

 lined by a distinct endothelium, but the veins are more lacunar in 

 character, and endothelial cells are absent from their walls. The 

 characters of the circulatory system are described in detail, and 

 attention directed to the discussion as to the closed or lacunar con- 

 dition of the vascular system of Molluscs. It is believed that the 

 differences in the results obtained depend not only on the imperfection 

 of certain methods of investigation, but also on the vagueness of the 

 ideas of some as to what is meant by a lacuna and a sinus. Although 

 the arteries end in vessels which are comparable to the capillaries 

 of vertebrates, they do not enter into a continuous connection with 

 venous vessels of similar histological constitution ; are the continua- 

 tions lacunae (or sinuses), or are they modified capillaries? If by 

 "lacunge" we mean spaces which, in a histological sense, have no 

 wall, then there are lacunte ; but if by the expression we mean to 



* SB. K. Akad. Wiss. Wien, Ixxxvii. (1883) pp. 237-301 (3 pis.). 



