OVULATION IN MAMMALS. 24/ 



pendent occurrence of ovulation and pairing, by Gerlach ('06), 

 who denied such Independence, and by Lams and Doorme ('07), 

 who state that ovulation In the mouse Is perhaps connected with 

 pairing. 



Bischoff ('44) did a little work with rats, and he came to the 

 conclusion that In them ovulation could take place without pair- 

 ing, but he confessed that his evidence was Incomplete. 



In view of these uncertain and conflicting statements, it has 

 seemed desirable to submit the matter of the relation, if any, 

 between ovulation and pairing, to a critical test in the case of 

 the rat and the mouse, using. In some instances, individuals that 

 had been isolated from as early a period as the sex could with 

 certainty be externally determined. The four female white mice 

 used were virgins from two litters, by different parents, and 

 were kept apart from all males. Including their brothers, from 

 the time they were two weeks old. Three of these females 

 were born In the laboratory in the middle of December, 1908, 

 and the other early In January, 1909, and all four, until they had 

 been weaned, were Isolated with their respective mothers. 



One of the virgins born the previous December was chloro- 

 formed on March 19, 1909, a day selected by chance, without 

 any special calculation other than the general knowledge that the 

 mice born about the same time as the test animals were beginning 

 to show signs of pregnancy. When the body of this animal was. 

 opened, and the ovaries examined, bright red spots were found 

 upon both these organs, a characteristic sign that ovulation had 

 recently occurred. The ovaries and Fallopian tubes were then 

 removed from the body, and serial sections were prepared in a 

 manner described in a previous paper (KIrkham '07). The study 

 of this material has revealed seven eggs In the Fallopian tubes, 

 beside numerous eggs still in the ovaries, the latter undergoing 

 degenerative changes after having formed the first polar body 

 and second polar spindle. The tube eggs appear In every respect 

 like those obtained from females which had paired, and were 

 then killed before the spermatozoa had reached the eggs. A 

 varying number of follicle cells are found associated with the eggs, 

 the zona pellucida In all cases Is sharply defined, all the eggs 

 possess second polar spindles, and In two Instances the first polar 

 body Is still visible, although decidedly atrophied. 



