294 SUMMARY OF CURRENT RESEARCHES RELATING TO 



without lamellae. Behind the junction of the two roots of the aorta, a 

 strong cceliac artery arises, which takes the blood to the posterior end 

 of the intestine ; it divides into lateral branches, which sub-divide, and 

 end in the intestinal epithelium, which is feebly developed. There is 

 rectal respiration, and air may also enter by the mouth. The arterial 

 blood passes by the portal vein to the liver, and the jugular veins also 

 bring back arterial blood from the pharyngeal wall and reduced gills. 



Respiratory Processes in Fishes.* — G-. van Rynberk has studied 

 the mechanism of respiration in dog-fish {Scyllium). In the first act 

 there is a simultaneous opening of mouth and spiracles, by which the 

 water enters, while the gill-clefts are closed. In the second act the 

 mouth and spiracles are closed, while the water passes out by the gill- 

 clefts. 



In the reflex expulsion, water may pass out from the buccal cavity 

 (a) by the mouth, if provoked by injurious stimuli ; (/3) by the spiracles, 

 if provoked by mechanical or other stimuli ; or (y) by the gill-clefts, if 

 provoked by mechanical stimuli of the gills, mucous membrane of the 

 clefts, or surrounding skin. 



There is a regular respiratory rhythm, which is peripherally deter- 

 mined, but is not exclusively due to contact with the water. 



Eyes of Periophthalmus and Boleophthalmus.f — W. Volz finds 

 that these fishes, which creep about on the tropical shore at low tide, 

 have, unlike other fishes, a well-developed power of vision when out of 

 water. The "campanule of Heller," serving for accommodation, is 

 absent, and so is the falciform process. They are replaced by a delicate,, 

 transversely striated muscle, lying outside of the scleral cartilage. It 

 extends towards the iris over the anterior part of the eye. When it 

 contracts, the lens is brought nearer the eye, and accommodation for 

 distant vision is thus effected. 



Comephorus.f — A. Korotneff gives a detailed account of the struc- 

 ture of this interesting fish from Lake Baikal. In addition to G. 

 baikaletisis, he describes a new species of G. dybowsM ; he found the 

 male of the latter, but that of the former species is still unknown. 



The pregnant females subsist on the abundant fatty mass surround- 

 ing the viscera. The gut is gradually atrophied, and becomes a thin 

 tube not more than 1 mm. in diameter. Both species die after re- 

 production. 



Carps and their Relatives.§ — Theodore Gill discusses the family 

 Cyprinidae, the " leather-mouthed fish " of Izaak Walton, of which over 

 a thousand representative species are known from Asia (especially India), 

 Africa, North America, and Europe. None are found in South America, 

 where their place is entirely taken by the Characinidse, and there are 

 none in Australia. The author summarises their characteristics, and has 

 interesting notes on their habits, life-history, sexual differentiation, and 

 familiar representatives, such as chub, dace, roach, rudd, minnow, and 



* Atti Rend. R. Accad. Lincei Roma, xiv. (1905) pp. 708-18 (7 figs.). 



t Arch. Sci. Phys. Nat , xx. (1905) pp. 579-80. 



X Wiss. Ergebn. Zool. Exped. Baikal-See, part 2 (Kiew, 1905) pp. 1- 39 (3 pis.). 



§ Smithsonian Misc. Collections, xlviii. (1905) pp. 195-217 (14 pis.). 



