32 SUMMARY OF CURRENT RESEARCHES RELATING TO 



consist of reticulate bundles of different thicknesses united together, 

 and all apparently consisting of cross-striped elements. The muscles of 

 the sinus-forming veins are grouped in bundles running in various 

 directions ; these are smooth -muscle elements. Between the auricles 

 and the ventricle is an intermediate zone in which neither cross-striped 

 nor smooth-muscle fibres are to be found. Nerves and nerve-cells occur 

 in the veins constituting the sinus, in the auricles, the ventricle, and 

 near the bulbus, and further there is a well developed network on the 

 upper surface of the bulbus. In the turtle the distribution is somewhat 

 similar, but the majority of the nerve-cells occur in the region of the liga- 

 mentum atrio-ventriculare, where this ligament joins on the ventricular 

 base and beside its origin in the auricles. The nerve-fibres run parallel 

 to the muscle-fibres and sometimes penetrate deeply between bundles. 

 The view is thereby suggested that a single nerve-fibre in its course 

 innervates several muscle-fibres and excites them to contraction. 



Production of Albinism and Melanism in Frogs.* — G. Tornier 

 has experimented with larvae of Pelobates fuscus, and finds that a 

 minimum diet of flesh results in albino frogs, that a maximum produces 

 melanism, and that reddish and greyish colours can be evoked at will 

 by regulating the food-supply. 



Fishes of Lake Baikal.f — L. S. Berg describes the skeleton of 

 Procottus jeittehi and other Cottidae from Lake Baikal, and discusses 

 the osteology of Cottocornephoridge and Cornephoridre. He gives a 

 synopsis of these three families of Baikal Cataphracti and discusses the 

 systematic position of the various types. A list is given of all the fishes 

 known to occur in the lake, ?>4 in all. Of these there are 17 which are 

 general in Siberian fresh waters, and 17 which are endemic. The en- 

 demic species may be divided into two sets, (a) those which are nearly 

 related to species widely distributed in Siberia (Sal mo alpinus eryfhrinus, 

 Coregonus migratorius, Thymallus arcticus bakalensis, Gottus kneri and 

 C. kessleri) ; (b) those which are quite unique (the sub-family Abysso- 

 cottini, the family Cottocornephoridas, and the family Comephorida?). 

 There are no forms in the Siberian waters, nor in the Arctic Ocean, nor in 

 the Pacific, which come near to these ; thus the absence of a post-clavicle 

 in the Baikal Cataphracti is distinctive. These peculiar forms live at 

 greater depths than any other fresh-water fishes, for they descend to 

 depths of 1600 metres. They are not, the author maintains, relicts of 

 previous geological periods, nor immigrants from the Arctic or the 

 Pacific Ocean, they are sui generis, and have arisen as such in Lake 

 Baikal during its long geological history. They are very ancient forms, 

 very divergent from typical Cottidas, and their resemblances to marine 

 forms are due to convergence. 



Buccal Incubation in Arius fissus.J — 0. and V. J. Pellegrin com- 

 municate some very interesting facts in connection with the care of the 

 young in this species from the coast of French Guiana, which may be 



* Zool. Anzeig., xxxii. (1907) pp. 284-8. 



f Zoolog. Untersuch. am Baikal-See, Lief. iii. (St. Petersburg and Berlin, 1907) 

 75 pp. (5 pis. and 15 figs.). 



X Comptes Rendus, cxlv. (1907) pp. 350-2. 



