20 SUMMARY OF CURRENT RESEARCHES RELATING TO 



As in the guinea-fowl, two sizes of spermatozoa are produced. The 

 transformation of the spermatid nucleus into the head of the spermato- 

 zoon comes about through the gradual concentration of the chromatin 

 into an elongated curved mass at one side within the nucleus, and the 

 subsequent elongation of this mass. 



Vitality of Spermatozoa.* — C. Fleig has made many experiments 

 as to the survival of human spermatozoa in various fluids. After being 

 " washed " in a centrifugal machine with much fluid — to get rid of albumin 

 — spermatozoa will live in mineral waters or sea-water for two or three 

 days. The presence of lime-salts seems to be necessary for sustained 

 movement. If the mineral water is placed in a refrigerator, the 

 spermatozoa remain alive for five or six days after emission. In the 

 case of pure seminal matter put into the refrigerator, there was re- 

 vivification of spermatozoa after eight days. 



Hyperdactylism in Fowls. f — D. Barfurth experimented with 

 Orpingtons, normally 4-toed, which exceptionally produce 5-toed forms. 

 Seven hyperdactylous hens (two years old) were paired with a normal 

 cock of the same age, and of the 152 chickens produced between May 

 and July 1908, 80 were normal and 72 hyperdactylous. The influence 

 of the two parents is equal. 



b. Histology. 



Minute Structure of Food Canal in Cyprinoid Fishes.J — A. Pictet 

 gives a histological description of the alimentary tract in carp and tench and 

 other Cyprinoids. He gives an account of the buccal cavity, the gullet, 

 and the intestine. One of his general points is that the buccal epithelium 

 includes the same elements as the epidermis (flat cells, large caliciform 

 cells, and terminal buds), and that the same kinds of cells occur beyond 

 the gill-clefts to the end of the oesophagus. This would seem to 

 indicate that the boundary between the ectodermic stomodaeum and 

 endodermic mesenteron was very far back. 



New Mode of Nuclear Division^ — Enzio Renter describes w T hat 

 he calls merokinesis — a new mode of nuclear division observed in the 

 fertilised ovum and the larger blastomeres of a mite Pediculopsis 

 graminum. The nuclear content prepares for mitosis not as a unified 

 structure, but in the form of four independent parts or karyomeres, 

 each corresponding to the area of an individual chromosooie. These 

 nuclear parts divide with their membrane intact. The chief peculiarity 

 is that each karyomere, i. e., each nuclear part corresponding to a 

 chromosome, divides normally and regularly by itself. It may be a 

 phyletic stage in karyokinesis. 



Thymus of Reptiles. || — A. P. Dustin has made a detailed study of 

 this organ in twelve species of tortoises, snakes and lizards. As to 

 the development, he finds that the small thymus cells arise directly 



* C.R. Soc. Biol. Paris, lxvii. (1909) pp. 162-4. 



t Arch. Entwickmech., xxvi. (1909) pp. 631-50. See also Zool. Zentralbl., xvi. 

 (1909) pp. 425-6. % Revue Suisse Zool., xvii. (1909) pp. 1-78 (2 pis.). 



§ Acta Soc. Fermica, xxxvii. (1909) pp. 1-52 (40 figs.).; 

 1| Arch. Zool. Exper., ii. (1909) pp. 43-227 (5 pis.). 



