258 SUMMARY OF CURRENT RESEARCHES RELATING TO 



b. Histologry. 



Taste-buds of Elasmobranchs. — Margaret H. Cook and H. V. 

 Neal {Jburn. Comp. Neurol., 1921, 33, 45-63, 29 figs.). Taste-buds in 

 Sqiialus acanthias are limited to the pharynx, where thej are distributed 

 over the floor, the roof, and the gill pouches. Their structure is liJse 

 that in other forms. They are groups of slender cells slightly raised 

 above the surface into a papilla. Each cell bears, externally, a hair-like 

 process, and is connected internally with a nerve ending. These taste- 

 bads are derived from the endoderm. They develop from the epithelial 

 lining of the pharynx which at all stages shows itself as endodermic. 

 There is no indication at any period of development of a migration 

 inward of the ectoderm, except the slight invagination which forms the 

 dental ridge. The pharyngeal scales arise in late embryonic stages. 

 They resemble placoid scales in structure, but are derived from the 

 endodermic lining of the pharynx. J. A. T. 



Periodic Nuclear Division in the Cat.— C. E. Droogleever 

 FoRTUYN VAN Leijden {Proc. Section of Sciences R. Acad. Amster- 

 dam, 1917, IS, 38-44). In explanation of the small number of mitoses 

 usually seen in growing tissues, it has been suggested by Child and by 

 Paterson that this is because amitotic divisions occur. It is here noted, 

 however, that for the mesentery, the outer stratified epithelium of the 

 cornea, and the epithelial ceils of Lieberkiihn's crypts in newborn cats, 

 a periodicity occurs in the mitotic nuclear division. There is a maxi- 

 mum in the evening, the night, and the early morning hours. There 

 is a minimum in the later morning hours and the early afternoon. The 

 maximum number of karyokineses does not always occur at the same 

 time, but it is never in the daytime. The minimum is always in the 

 middle of the day. If this is a general fact it may explain why in 

 general in growing tissues few karyokineses are seen. For the fixing of 

 tissues is usually effected in the middle of the day. J. A. T. 



. Striped Muscle of Pulmonary Veins of Rat. — F. Granel {Comptes 

 Rendus Soc. Biol., 1921, 84, 291-4). Stieda reported the presence of 

 striped muscle of a cardiac nature in the trunk of the pulmonary \eins. 

 Granel has studied this in Mus decumanus, and finds that in structure 

 and in development it is closely allied to cardiac muscle, of which it is 

 an extension. There is an internal longitudinal or oblique layer, and 

 an external circular layer, both striped. There is a delicate connective 

 lamella between the two layers, and the muscular sheath is rich in 

 vessels and nerves. J. A. T. 



Parasomes in Pancreas of Tadpole of Rana temporaria.— 

 R. HovASSE {Conines Rendvs Soc. Biol, 1921, 84, 190-1). In a 

 tadpole developed parthenogenetically most of the cells of the pancreas 

 showed numerous parasomes, sometimes seven in one cell, either isolated 

 in the cytoplasm or grouped within a larger parasome near the nucleus. 

 Such parasomes have tc do with the formation of fats, but there was 

 little fat in the food. The significance of their occurrence in this case 

 is obscure. J. A. T. 



