SUMMARY OF CURRENT RESEARCHES 



RELATING TO 



ZOOLOGY AND BOTANY 



(principally invertebrata and cryptogamia), 



MICEOSCOPY, Etc.* 



ZOOLOGY. 



VERTEBRATA. 



a, Embryolog-y.f 



Statistical Study of Sex-cells.J— B. M. Allen has made a study 

 of this kind on embryos of Chrysemys marginata. Some of the points 

 elucidated may be noticed. The total numbers of sex-cells were found 

 to be similar in the early and in the later stages, proving that there is 

 no cell-division during these periods. The sizes of the embryos varied 

 from 2 • 8 mm. to 8 mm. The first clear indications of the division of 

 the sex-cells are found in an embryo 10 mm. long, and specimens some 

 stages later than this show no division. It thus appears that the stage 

 at which the sex-cells begin to multiply varies within pretty wide Hmits. 

 This result agrees with the conclusions of Eigenmann and Beard. Beard's 

 conception of a specific number of sex-cells, expressed by the formula 

 2" - 1, during these early stages is not borne out by the facts observed in 

 Chrysemys, in which the number ranges from 302 to 1744. As to the 

 migration of the sex-cells, it is noted that upon an average 47 • 7 p.c. 

 reach the sex-glands, while the remainder come to rest in the alimentary 

 tract, the mesentery, and the region between the root of the mesentery, 

 the aorta, and the mesonephros. An interesting point is that in the 

 case of double monsters arising from the same egg, each of the embryos 

 has a normal number of sex-cells. 



Inheritance of Coat-pigments and Coat-patterns in Rats and 

 6uinea-pigs.§ — H. MacCurdy and W. E. Castle state that the results 

 of selection brought to bear upon the coat-pattern are seemingly very 



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

 do not hold thenfiselves 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. 



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 Anat. Anzeig., xxx. (1907) pp. 391-9 (5 figs.). 



§ Carnegie Inst, of Washington, Publication No. 70 (1907) 50 pp. 



