ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 661 



course does not explain the case of the Physoclysti. He has not been 

 able to demonstrate how the fishes extract the air from the water enter- 

 ing their mouths. 



Swim-bladder of Fishes.* — E. E. Prince discusses the structure and 

 relations of the swim-bladder in different types of fishes, and advances 

 the view that it is a degenerate gland whose original use is gone. The 

 interpretation of the swim-bladder as a glandular structure best accords 

 with its character in the embryonic and larval stages. The suggestions 

 that it is of use for helping in flotation, or in respiration, or in hearing, 

 are dismissed as insufficiently established. It may be that the storage 

 of nitrogen, secreted from the blood circulating in the vascular network 

 of the swim-bladder, may be associated with states of dormancy or of 

 inanition, or some marked change in the character of the food. 



The " Oval " of the Swim-bladder.t — J. Nusbaum and Caroline 

 Beis furnish additional evidence that disruptive changes in the cells of 

 the epithelial body produce the gas in the swim-bladder. In Fierasfer, 

 Macropods, etc., the epithelial body is an active gas-secreting gland. A 

 study of species of Ophidium and Lurioperca shows that the so-called 

 " oval " functions as an elastic pressure-adjusting organ. By expanding 

 and contracting it increases or decreases the density of the gas in the 

 swim-bladder. In Ophidium rochii there is an interesting mechanical 

 device abetting this function of the oval. 



Breast-bone in Cyprinus carpio.J — W. B. von Baehr has investi- 

 gated the question of the existence of a breast-bone in carp as described 

 by Eimer. In old carp he finds an apparently cartilaginous hard forma- 

 tion in the position of a breast-bone, connected by several similar pieces 

 to the bony ribs. In young carp these pseudo-skeletal parts are seen to 

 be of the nature of connective tissue, and not cartilaginous. In Barbus 

 vulgaris they are not present. In any case no real homology based on 

 the relation to the ribs can be established ; functionally, however, the 

 pseudosternum is analogous to the sternum of higher animals. 



Morphology of Teleostean Skeleton.§ — D. N. Koschkaroff describes 

 a series of typical examples of the Siluridas. His general conclusion is 

 that the group is undoubtedly a natural one. The question of the rela- 

 tionship of the family to other Teleosts is not answered, but a number 

 of similarities between the Silurida? and Cyprinidas are pointed out. 

 These are : — (1) both have a Weberian apparatus ; (2) both possess a 

 long olfactory canal ; (3) in both the skull cavity is continued far 

 forward, and ali- and orbito-sphenoid form its walls ; (4) a few Cypri- 

 noids possess a fontanelle separating the frontals similar to that of 

 Siluroids ; (5) in both the fifth segment of the skull ossifies completely 

 and is covered above by an unpaired bone, the supra-ethmoidean. There 

 remains the difficulty of the typical fish-scales of the Cyprinoids, w r hich 

 cannot be conceived as derived from the Siluroids. It is probably a case 

 of convergence. 



* Proc. and Trans. Nova Scotia Inst. Science, xl. (1906) pp. 199-226 (4 pis.). 

 t Bull. Internat. Acad. Sci. Cracovie, No. 10 (1905) pp. 778-84 (4 figs.). 

 % Zool. Jahrb., xxii. (1906) pp. 629-36 (1 pi.). 

 § Bull. Soc. Imp. Nat. Moscou, xix. (1905) pp. 209-307 (1 pi.). 



