164 SUMMARY OF CURRENT RESEARCHES RELATING TO 



is differentiated into clitoris and clitorium. The urogenital orifice is not 

 to be characterised as the sexual groove. The edges of the orifice 

 develop into the labia vulval. The sex-thickenings do not become labia 

 vulvae, but come to lie in front of the clitoris and completely alter in 

 appearance. 



Studies on the Islands of Langerhans.* — K. Helly has made some 

 investigations on the development and structure of these bodies, and 

 concludes that they are present in all the vertebrate groups. They are 

 organs sui generis, and as such fundamentally different in histological 

 structure from the true pancreas. In development they arise from an 

 epithelium which is not specifically differentiated as pancreas. No 

 transitions between the two types occur at any period of their develop- 

 ment, nor in the mature condition. Consequently, the view that they 

 represent a kind of reserve material for the regeneration of the pancreas- 

 cells cannot be held. It will be observed that these views are, on the 

 one hand, markedly oppossed to those of Dale, while, on the other, they 

 confirm the work of Diamare, Rennie, and others. 



Club Cells in Epiderm of Fishes. f — M. Oxner has investigated the 

 form, distribution, origin, and function of the peculiar club cells oc- 

 curring in the epiderm of Cyclostomes and bony fishes. Within the 

 Teleostei they are found in Physostomi (except Salmonidas) ; they 

 may be present or absent in very nearly-related families. It is not 

 certain whether the formations occurring in Gadidae and a few marine 

 Acanthopterygii are to be regarded as true club-cells. In the genera in 

 which they are present, they occur in the whole covering layer, with the 

 limitation that they are always absent on the barbules and, with few 

 exceptions, on the skin of the lips. Where they occur on the lips, they 

 extend also to the epithelium of the tongue, of the mucous membrane 

 and even of the pharynx of very young individuals. The distribution 

 is not at all regular. They are most numerous on the head and neck 

 region, and fewest on the pectoral and caudal fins. They are special 

 unicellular gland-cells of protective function, they are able to form a 

 kind of scurf over a wound, in eels they act as excretory glands, and 

 they appear to have other functions as well. 



b. Histolosry. 



Neurological Studies. — Kurt Goldstein $ gives an account of the 

 structure of the brain of Teleostean fishes, especially of the cerebral 

 hemispheres and thalamencephalon. 



Kurt Berliner § discusses the minute structure and the development 

 of the cerebellum in various Vertebrates. 



Structure of Amphibian Red Blood Corpuscles. || — Fr. Weidenreich 

 has studied the erythrocytes of the salamander and the frog. There is a 

 distinct cellular membrane, but no demonstrable plasmic structure. The 

 erythrocytes of amphibians differ from those of mammals in form and 



* Arch. Mikr. Anat., lxvii. (1905) pp. 124-41 (1 pi.). 



t Jena Zeitschr., xxxiii. (1905) pp. 589-646 (5 pis. and 1 fig.). 



t Arch. Mikr. Anat., lxvi. (1905) pp. 135-219 (5 pis. and 23 figs.). 



§ Tom. cit., pp. 220-69 (1 pi.). 



|| Tom. cit., pp. 270-98 (1 pi. and 2 figs.). 



