THE EGG OF THE DOMESTIC CAT 145 



If kittens are taken away from a cat within a few hours of their 

 birth, the mother may come in heat again from three to six weeks 

 after parturition, a fact which is in substantial agreement ^\ith 

 those noted by Winiwarter and Saintmont ('08). 



Ovulation 



Ancel and Bouin ('09) distinguish between mammals with 

 spontaneous ovulation, and those in which it is provoked by cop- 

 ulation. In the first class thej^ place the primates, including man, 

 and in addition the dog, horse, cow and pig. All of these are 

 probably properly classified; in fact any animal which can be 

 artificially impregnated may be placed in this group. In the 

 second class they include the rabbit, guinea pig, mouse and cat. 

 With respect to the mouse, their classification is incorrect, Sobotta 

 ('95) and Kirkham ('07) having proven that the ovulation of 

 that animal is independent of pairing. Regarding the ovulation 

 of the rabbit and guinea pig there has been difference of opinion 

 among those who have investigated the matter. It would seem 

 probable that the rabbit is correctly (Heape '05), and the guinea 

 pig incorrectly placed in the second class (Rubaschkin '05). 

 The ferret also belongs in the second group (Marshall '04). 



In a preliminar}^ note ('10) the writer has already been able 

 to confirm the statement of Ancel and Bouin with respect to the 

 ovulation of the cat, a statement previously made by Winiwarter 

 and Saintmont ('08). The evidence will follow in detail, and is 

 summarized in fig. 1. 



Of a series of ten females killed at periods ranging from 23 to 

 50 hours after pairing, six had ovulated, and another, the first 

 in the series, would certainly have done so within the longer time, 

 if one may judge at all from the condition of the largest follicles 

 in her ovaries. On the contrary, in a second series of five animals, 

 not allowed to pair, none had ovulated within 50 hours, nor indeed 

 within a much longer time, after being observed first to be willing 

 to pair. 



One animal in the second series, allowed to live one week after 

 the close of an observed period of heat of six daj^s, showed three 



