708 SUMMARY OF CURRENT RESEARCHES RELATING TO 



which the contents of the intestine were made to pass through the shell- 

 gland. The result led them to conclude that the stimulus which excites 

 the shell-secreting glands of the fowl's oviduct into activity is mechanical 

 rather than chemical in nature, and that the formation of the shell is 

 brought about by a strictly local reflex, and is not immediately dependent 

 upon the activity of other portions of the reproductive system. 



Ovarian Interstitial Gland in Rabbit.* — CI. Regaud and G. 

 Dubreuil find that if a doe be isolated the interstitial gland diminishes, 

 —greatly in winter, less in spring. Permanent cohabitation with a 

 virile male determines an increase in the gland, even during winter. 

 Variations in general nutrition do not account for the changes in the 

 gland. The sexual activity in spring and cohabitation are both associated 

 with increased development of the gland. 



Spermatogenesis of Guinea FowLf— M. F. Guyer has studied the 

 spermatogenesis of the domestic form of Numida melmgris. Seventeen 

 chromosomes, differing considerably in size, occur in the spermatogonia. 

 Nine chromosomes appear for division in the primary spermatocytes. 

 Of these, eight are presumably bivalent, the other, which is comparable 

 to the " accessory " or " odd " chromosome of Tracheata, remains 

 unpaired. 



The odd chromosome passes undivided to one pole of the spindle 

 considerably in advance of the other chromosomes. The result of the 

 division of the primary spermatocyte is, therefore, that half of the 

 daughter-cells contain eight, and half nine chromosomes. 



The eight chromosomes which pass to the one secondary spermato- 

 cyte pair again to form four, which ultimately appear at the time of 

 division in this cell. Eight of the nine which pass to the other 

 secondary spermatocyte pair similarly, the odd one remaining unpaired. 

 At the division of the secondary spermatocyte, the odd chromosome 

 after lagging for some time divides longitudinally. 



The divisions of the secondary spermatocytes result in the production 

 in equal numbers of two classes of spermatids, those containing the odd 

 chromosome and those without it. The two kinds of spermatids are 

 visibly different, and ultimately give rise to spermatozoa which differ in 

 size. The axial filament of the spermatozoon tail apparently arises in 

 contact with the nucleus. 



b. Histology. 



Variability in Number of Chromosomes.} — Paolo Delia Valle has 

 studied the chromosomes, especially in larval salamanders, with particular 

 reference to their number and individuality. He finds that the number 

 is by no means so constant as is usually said. It is variable within 

 limits, and these are wider for the somatic cells than for the germ-cells. 



Nervous System of a Deaf White Cat.§— C. Winkler has studied 

 the nervous system of a white blue-eyed cat, which during life, though 



* C.R. Soc. Biol. Paris, lxvii. (1909) pp. 348-50. 



t Anat. Anzeig., xxxiv. (1909) pp. 502-13 (2 pis.). 



% Arch. Zool, iv. (1909) pp. 1-177 (1 pi.) 



§ Proc. Acad. Amsterdam Section of Sciences, xi. (1909) pp. 225-30. 



