177 



SUMMARY OF CURRENT RESEARCHES 



EEt,ATLNG TO 



ZOOLOGY AND BOTANY 



(principally invertbbrata and cryptogamia), 



MICBOSCOPY, Etc.* 



ZOOLOGY. 



VERTEBRATA. 



a- Embryologry.t 



Oogenesis in Chick4— Charles H. Swift has inquired into the 

 origin of the definitive sex-cells in the female chick and their relation 

 to the primordial germ-cells. During the two days subsequent to the 

 development of the germinal epithelium (between eightieth and ninetieth 

 hours of incubation), a majority of the primordial germ-cells are found 

 between the cells of that tissue. Some of the remaining primordial 

 germ-cells are present in the mesenchyme beneath the germinal 

 epithelium, others are found in the cords of urogenital union, still 

 others remain in the root of the mesentery. The latter may be seen 

 in that situation in some embryos until the ninth day of development, 

 when they degenerate. During the fourth and fifth days of develop- 

 ment it may be seen that the number of germ-cells on the left side 

 exceeds that on the right in the proportion of 2-5 to 1. 



During the sixth and seventh days of development the germinal 

 epithelium sends down into the subjacent tissue a first series of sex- 

 cords or cords of first proliferation. These cords are produced as a 

 result of localized activity of the germinal epithelium. The cords of 

 first proliferation are epithelial in character, and the germ-cells, which 

 are present in them, do not seem to have anything to do with their 

 formation. But it is possible that some germ-cells stimulate the 

 epithelial cells around them to activity. The cords of first proliferation 



* The Society are not intended to be denoted by the editorial" we," and they 

 do not hold themselves responsible for the views of the authors of the papers 

 noted, nor for any claim to novelty or otherwise made by them. The object of 

 this j)art of the Journal is to present a summary of the papers as actually pub- 

 lished, and to describe and illustrate Instruments, Apparatus, etc., which are 

 either new or have not been previously described in this country. 



t This section includes not only papers relating to Embryology properly so 

 called, but also those dealing with Evolution, Development, Reproduction, and 

 allied subjects. 



X Amer. Journ. Anat., xviii. (1915) pp. 441-70 (8 figs.;. 



