ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 413 



acid secretion which acts on the carbonate of lime of the star-fish 

 host. There is one gill. The adult has a shell about 1 centimetre 

 long, and is, on the whole, like Ancylus ; it appears to belong to the 

 genus Concholepas. 



The presence of the entoparasitic form may be recognized by a 

 conical swelling on the arm of a Linchia, and close examination will 

 reveal the presence of a small round hole from which the apex of 

 the shell of the gastropod projects ; it is without doubt a Stylina. 

 The adult shell is a centimetre long and has eight coils ; it has an 

 extraordinarily long and muscular proboscis, which may extend for 

 1 • 5 cm. At the base of the proboscis is a false mantle which clearly 

 acts as a respiratory pump. The proboscis itself extends along the wall 

 of the coelom of its host ; there is no pharynx and no radula. Nor is 

 there any operculum. There are eyes and auditory vesicles, but no 

 tentacles ; the sexes are separate, and the genital products appear to 

 escape into the sea. Only about two per cent, of the Linckiae are 

 troubled by these parasites. Further details and figures are promised. 



Spawning of Doris.* — By carefully watching the eggs as they 

 passed down the oviduct, M, E. Bolot was able to ascertain the 

 function of the various regions of the " albuminous gland " of Boris. 

 The eggs were seen to receive their various coats in different regions 

 of the gland, which is therefore really made up of glands which in 

 other gastropods are usually separated from one another. The 

 fertilized ovum enters a large canal beset with branching tubes, 

 which are lined by large irregular nucleated cells ; this region is the 

 true albuminous gland, where the first coat is deposited round the 

 ovum. In the next part of its course the shell is deposited in the 

 " shell-gland," the cells lining which differ from the albuminous cells 

 only in their smaller size. These two regions constitute Hancock's 

 " opaque portion " of the albuminous gland. Following this is the 

 "jelly-gland," made up of convoluted tubes, forming the external 

 edge of the whole gland ; the cells lining this region are elongated, 

 very granular, and arranged in a single layer ; they deposit a jelly 

 (" masse glaireuse ") which binds the eggs together in a cylindrical 

 string, which passes into a slit-like cavity and passes out of the body 

 as a ribbon-shaped string. It is possible to separate the eggs of 

 Doris from this jelly, when laid, by carefully acting on them with 

 acetic acid. D. testudinaria is remarkable amongst Nudibranchs for 

 possessing a " prostate " on the vas deferens, such as occurs in other 

 gastropods. 



Central Nervous System of Tethys leporina.t — Prof. H. do 

 Lacaze-Duthiers points out that the difficulty with regard to the 

 central nervous system of Tethys lies not in the topography of its 

 lozenge-shaped central mass, but in the interpretation of the morpho- 

 logical value of its constituent parts. He regards it as being com- 

 posed of three groups of ganglia ; the cells of which it is made up 

 are contained in pyriform sacs, arranged in a racemose fashion • the 

 largest pouches are central and inferior, the smallest on the superior 



* Comptes Rendus, cii. (1886) pp. 829-31. f Ibid., ci. (1885) pp. 135-9. 



