ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 585 



while the principal nerves with which they are continuous are almost 

 always united by transverse commissures. 



4. The pallial ganglia are always more or less intimately con- 

 nected with the pedal ganglia. 



The two first of these sets of characters are regarded as being 

 primitive in nature. Some of the facts here brought forward are in 

 opposition to the statements of M. Bela Haller, who denies the 

 presence of the proboscidian commissure described by Lacaze- 

 Duthiers in Haliotis tuberculata. M. Bouvier is able to support the 

 statement of the French anatomist on this and other points traversed 

 by M. Haller. 



Retina of Helix pomatia* — In a further communication on tbe 

 structure of the optic organ, Prof. J. Carriere describes the retina 

 of this common snail. The method of examination employed was to 

 cut off the tip of the tentacle with the eye, to expose it for a few 

 minutes to tbe vapour of 1 per cent, osmic acid, and colour with 

 ' picrocarmine. The removal of the pigment was effected by very dilute 

 eau de Javelle, but this is an operation which must be performed 

 with great care. Sections of about ■ 005 mm. thickness were made. 



The colourless cells were found to be flask-shaped, and to 

 have contents which were not stained either by picrocarmine or by 

 beematoxylin, but with osmic acid hardened to a clear grey mass 

 which completely filled the cell, and rose above it as a convex 

 swelling. No differentiation was to be noticed within the mass ; 

 when the convex boundary was distinct, the cell was divisible into a 

 retina and hardened lens, but in other cases the cell-contents ap- 

 peared to pass directly into the lens. The colourless cells are not 

 regularly polygonal but intercalated among the pigmented, so that 

 they present all stages between an irregular polygon and a star; 

 their lateral processes entered as far as the pigmented cells. The 

 pigmented cells are not filled with pigment, a narrow axial cord being 

 free from it; when the pigment is removed the cells are seen, on 

 staining with picrocarmine, to have a homogeneous transparent 

 grey cell-body, which is very different to the reddish-yellow contents 

 of the flask-shaped cells ; there is a highly refractive axis which 

 corresponds to the bright spot seen in pigmented cells, from which 

 tbe colour has not been removed. In some points the author ditfers 

 from the results recently published by Hilger. 



Organization of Phcenicurus. — Dr. E. S. Bergh f has addressed a 

 letter to Prof. H. de Lacaze-Duthiers in which he expresses his opinion 

 that Phcenicurus is really a papilla of Tetliys ; he bases this view on 

 what he has himself been able to observe at Naples. The Professor, 

 in an extended essay,! adds to our knowledge of this form, on which 

 he has already published a note § ; in answer to his critic he points 

 out that no figure has ever been published by him or by those who 

 think with him, and reminds us that Dujardin stated in 1845 that 



* Zool. Anzeig., ix. (1886) pp. 220-3. 



t Arch. Zool. Expe'r. ct Gen., iv. (.1886) pp. 73-6. 



j Tom. cit, pp. 77-108 (2 pis.). § See this Journal, v. (1885) p. 1005. 



