ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 309 



retina includes three kinds of elements, — supporting cells, sensory cells, 

 and ganglion-cells, besides a layer of nerve-fibres in its lower portion. 

 There is no lens, and the pellucida cannot act as such, but the spherical 

 hyaline outer terminations of the sensory cells have probably this 

 function. In other words, each sensory cell has its own lens. The 

 entire structure cannot be called rudimentary, though it obviously 

 represents a different phyletic stage from that seen in Sphenodon, where 

 the parietal organ is a " cameral " eye, with a cjncave retina and a lens. 



Single and Twin Cones in Retina of Fishes.* — Messrs. C. H. 

 Eigenmann and Gr. D. Shafer discuss the mosaic of single and twin 

 cones. The arrangement of these is remarkably constant for any given 

 species, but differs considerably in different groups. Yet the patterns 

 in all of the species examined can be arranged in a series. 



Cilia in Convoluted Tubules of Mammalian Kidney .f— Prof. E. 

 Wace Carlier notes that the fact that the cells lining these tubules are 

 ciliated seems to have been lost sight of in Britain, though many Con- 

 tinental investigators have studied the subject. He brings forward 

 evidence from many mammals showing that the presence of cilia as a 

 normal constituent of the secreting cells of the convoluted tubules is 

 an undoubted fact. In another communication | he shows that the 

 human kidney is no exception. 



Structure of Lungs in Birds.§ — Dr. F. Supino points out that the 

 lung of birds does not exhibit large polyhedral alveoli, as Panceri de- 

 scribed, nor an inextricable network of intercommunicating bronchioles, 

 as Sappey described, but exhibits very numerous bronchioles each one 

 of which dilates to form its own little alveolus. 



Sensory Pits of Crotalin3e.|| — Mr. G. S. West has studied these 

 structures in various crotaline snakes. They are to be regarded as 

 tegumental sense-organs of the lateral line series, and consist of two , 

 chambers, an outer and an inner, separated by a partition or pit-mem- 

 brane. Each chamber communicates with the exterior, but the inner one 

 by a minute aperture only. The pit-membrane is a sensory structure, 

 and is liberally supplied with nerves (branches of v.) and blood-vessels. 

 In development both chambers arise by invaginations of the epidermis. 

 Nothing is known of their function. 



Retina of Amphibians.!] — Mr. H. M. Bernard has investigated the 

 minute structure of the retina in the frog and other Amphibians, em- 

 ploying such fixatives as boiling corrosive acetic acid, the animal having 

 been kept and killed in darkness. He finds that the cones of the retina 

 " are not elements with any special sensory function, as was maintained 

 by the earlier investigators, but that they are simply stages in the 

 development of fresh rods ; and that, in addition to their potential 

 value as future rods, they serve, even in their earliest stages, to keep 



» Amer. Nat., xxxiv. (1900) pp. 109-18 (19 figs.). 



t Proc. Scot. Micr. Soc., ii. (1898-9) pp. 243-51 (1 pi.). 



J Tom. cit, pp. 275-7 (2 figs.). 



§ Atti Soc. Venet.-Trent. Sci. Nat., 1898 (published 1899) pp. 306-15 (1 pi.). 



|| Quart. Jouru. Micr. Sci., xliii. (1900) pp. 49-59 (1 pi.). 



1 Tom. cit., pp. 23-47 (1 pi.). 



