ZOOLOGY AND BOTANY, MICROSCOPY, ETC. ITT* 



to the steadily increasing literature of this subject. He discusses the 

 work of earlier writers, and seeks to bring his own into line with it. He 

 has experimentally demonstrated the hydrostatic function of the organ, 

 but cannot say if it is an active one — whether the quantity of gas is 

 capable of being lessened or increased at need — or whether mechanical 

 as a result of its position. The composition of the gases receives 

 attention, and also the nerve supply and structure of the bladder, 

 particularly the blood vessels and gland cells. In the blood glands there 

 are remarkable giant cells, resembling those of the bone marrow. On a 

 surface view these are seen to be disposed irregularly, and are so large 

 that they frequently occupy the whole thickness of the cellular layer of 

 the gland. Each cell is beset by a close network of vessels. These cells 

 are particularly numerous in young fishes, and they' appear to give rise, 

 by amitotic division of the nucleus, to the small cells of the gland. 



Swim-Bladder of Fishes.* — A. Jaeger finds that there are three kinds 

 of arrangement in the swim-bladder of fishes for regulating the quantity 

 of gas. The " red-body " liberates oxygen (which is the only element to 

 be considered in an increase of air in the bladder) from the blood. The 

 lessening of the quantity of air is effected in fishes with closed bladder 

 through the absorption of oxygen by means of the " oval," in others 

 with open bladder by its escape through the duct. The inner epithelial 

 lining of the bladder is impermeable to oxygen. Through the regulating 

 mechanism described, the changing water-pressure is neutralised so that, 

 at all depths, the volume of the fish is the same, and its specific gravity 

 equal to that of the surrounding medium. 



Inferior Pharyngeal Bones in Genus Orestias.f — J. Pellegrin 

 finds considerable differences in the character of the teeth in different 

 species of this genus, which are adaptations to diverse feeding habits. 

 A specialised food, composed of small strong-shelled molluscs which are 

 difficult to crush, has led to the transformation of narrow alveolar 

 surfaces into conical teeth, with considerable augmentation of the alveo- 

 lar surface. In species which feed on softer vegetable or animal 

 substances, there are large alveolar surfaces, with granular rounded teeth, 

 and a marked tendency to fusion of the inferior pharyngeals. 



Australian Fossil Fishes. J — F. Chapman and G. B. Pritchard give 

 an account of eleven genera, represented by twenty-five species of Tertiary 

 Selachia, three of which are new. The ranges of the several forms are 

 tabulated, and some interesting information, pointing to the affinity of 

 the Cretaceo-Tertiary strata of New Zealand and Australia, is adduced. 



Food-Fishes of North Sea.§ — P. P. C. Hoek, in collaboration with 

 Heinckc, Ehrenbaum and Kyle, has given an account of the ten most 

 important food-fishes of the North Sea. Each species is dealt with 



* Ber. Senckenberg Nat. Ges. Fr. (1904) pp. G3*-72*. 



t Comptes Rendus, cxxxix. (1904) pp. 682-4. 



J Proc. Roy. Soc. Vict., xvii. (1904) pp. 267-97 (2 pls.\ 



§ Die Literatur der zehn wicbtigsten Nutzfischc d^r Nordsee in monojjraphischer 

 Darstellung. Conseil Intemat. Explor. de la Mer. No. 3 (1903) pp. 112 (10 pis.). 

 See Zool. Zentralbl., xi. (1904) pp. 852-3. 



