SUMMARY OF CURRENT RESEARCHES 



RELATING TO 



ZOOLOGY AND BOTANY 



(principally invertebrata and cryptogamia), 



MICEOSCOPY, Etc.* 



ZOOLOGY. 



VERTEBRATA. 

 a. Embryolog-y.t 



Origin of Sex-Cells of Chrysemys.l — Bennet M. Allen finds in 

 Chrysemys marginata the first appearance of primitive sex-cells in the 

 hypoblast at the edge of the area pellucida, in a zone extending on each 

 side from a point opposite the anterior portion of the pronephros, to a 

 point behind the embryo. 



They migrate within the endoderm to a point immediately below the 

 notochord, from which a large proportion of them continue upward in 

 the mesentery. The great majority of these reach the sex-gland primor- 

 dium in the peritoneum on each side of the root of the mesentery. 



In both ovary and testis, many of the sex-cells are carried into the 

 sex-cords, where they give rise to spermatogonia in the testis, and 

 probably degenerate in the ovary. In the testis most of the sex-cells 

 come to be in the sex-cords, while in the ovary the majority remain 

 in the germinal epithelium, there to become oogonia. Those that 

 remain in the peritoneum of the testis degenerate. 



The sex-cells lie among the peritoneal cells, but are not derived from 

 them. No essential differences in origin or character were to be 

 observed between oogonia and spermatogonia. 



History of Division Centres in Fertilisation^ — K. Kostanecki 

 has inquired into the question of the origin of the division centres of 

 the first segmentation spindle in fertilisation. For research material he 

 used Myzostoma glabrum, and from his results here and from other 



* 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 part 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. 



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

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

 allied subjects. 



% Anat. Anzeig., xxix. (1906) pp. 217-36 (15 figs.). 



§ Arch. Mikr. Anat., lxviii. (1906) pp. 359-431 (2 pis.) 



