23 



SUMMARY or CUPiEENT RESEARCHES 



BELATING TO 



ZOOLOGY AND BOTANY 



(principally invertebrata and cryptogamia), 



MICEOSCOPY, Etc.* 



ZOOLOGY. 



VERTEBRATA. 



a. Embryolog'y, Evolution, Development, Reproduction, 

 and Allied Subjects. 



Ovary of Spermophile. — Della Drips {Amer. Journ. Anat., 191D, 

 25, 117-84, 28 figs.). In Spermophilus citellus tridecemline((tus ovula- 

 tion occurs once a year, during the rutting season in early spring. 

 Ovulation is dependent on coitus. The corpora lutea are not present 

 in the ovaries at the rutting time ; they develop and pass through their 

 cycle whether fertilization follows or not ; while they are present in the 

 ovaries the process of developing and ripening the follicles is at a 

 standstill. The corpora lutea do not seem to influence the mammary 

 gland. The luteal cells are the transformed granulosa cells of the 

 follicle. There is evidence that the corpus luteum has two internal 

 secretions, each with its specific effect on the uterus, one bringing about 

 the changes incident to pregnancy, and the other effecting the normal 

 involution of the organ. The corpora lutea, fix the period of oestrus by 

 preventing the development and ripening of follicles until the time for 

 the next rutting season is at hand. J. A. T. 



'» 



Identical Female Twins in Pigeons from Ova of High Storage 

 Metabolism. — Oscar Riddle {Journ. Exper. Zool, 1918, 26,227-54). 

 The author has previously maintained that male pigeons arise from eggs 

 (yolks) of lesser storage metabolism (small size and higher metabolism), 

 and female pigeons from eggs (yolks) of greater storage metabolism 

 (large size and lower metabolism). He has now studied two cases of 

 female identical twins which appear to have been produced from ova of 

 high storage metabolism. The proof of this must be indirect, but it is 

 known, for instance, that the eggs which produced the female identical 



* The Society does not hold itself responsible for the views of the authors 

 of the papers abstracted. Ths object of this part of the Journal is to present 

 a summary of the papers as actually published, and to describe and illustrate 

 Instruments, Apparatus, etc., which are either new or have not been previously 

 described in this country. 



