THE MATURATION OF THE MOUSE EGG. 



WILLIAM B. KIRKHAM. 



Sobotta ('95) after careful study of a very large number of 

 preparations of the egg and ovary of the white mouse came to 

 the conclusion that in nine tenths of these eggs the maturation 

 processes involve the suppression of the first polar spindle, and 

 the formation of only a single polar body. Gerlach ('06), after 

 a study of preparations made at least as early as 1890, has re- 

 vived Tafani's theory that in the majority of mouse eggs the second 

 polar body is suppressed. Gerlach's conclusion is that when a 

 spermatozoon enters an egg sometime after it has formed the 

 second polar spindle, the second polar body fails to develop, and 

 the spindle degenerates within the egg. 



These results are at variance with the majority of opinions 

 reached, before and since, by investigators of the eggs of other 

 animals, vertebrate and invertebrate, and a reinvestigation of the 

 maturation processes in the egg of the white mouse has brought 

 it into line with most other metazoon eggs. 



Material and Method. The mice used have been killed dur- 

 ing the period of most active breeding, namely, April, May, June 

 and September, and serial sections made of the ovaries and Fallo- 

 pian tubes. Ovulation, during the spring months, occurs very 

 soon after parturition, independent of copulation, as observed by 

 Rubaschkin ('05) in the guinea-pig. 



When observed to be pregnant, the females were mated, and 

 killed, some a few days or hours before parturition, others during 

 that process, and still others at intervals from a few minutes to 

 thirty hours after giving birth to a litter. The tissues were killed 

 with a variety of the more generally used cytological fluids, and 

 the following is a brief summary of the results obtained : All 

 the ovaries contained some eggs with the second polar spindle 

 and accompanied by the first polar body, and a majority of the 

 series revealed ovarian eggs at the end of the spireme or with the 

 first polar spindle. The eggs observed in the Fallopian tube fall 

 into two main groups : those which had not been fertilized, and 



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