246 WILLIAM B. KIRKHAM. 



of his own, and Lams and Doorme ('07) quote Reichert alone. 

 The careful researches of Rubaschkin ('05), however, have defi- 

 nitely confirmed Bischoff 's original contention, and it may there- 

 fore be considered as finally settled that in the guinea-pig 

 ovulation and pairing are essentially independent phenomena. 



The rabbit's egg has been studied by Barry ('39), Bischoff ('42), 

 Coste ('47), Heap ('05), and by Dubreuil and Regaud ('08). 

 Barry, and the last three authors named above find, contrary to 

 Bischoff, that the rabbit cannot ovulate until a short time after 

 pairing has occurred, but Coste claims to have induced ovulation 

 by taking females which, isolated from males, had been in heat 

 for a number of days, and allowing males to cover them without, 

 however, allowing them to remain together long enough for actual 

 insemination to take place. Heape, and Dubreuil and Regaud, 

 on the contrary, find that if, in this animal, pairing for any reason 

 does not occur during the oestrus period, the eggs which would 

 naturally have been discharged all degenerate within the ovaries. 

 Indeed, according to Heape, if the male is withheld from the doe 

 during several consecutive periods of oestrus, most, if not all, 

 of the older and many of the younger follicles undergo degenera- 

 tion, and this may result in a more or less permanent sterility. 



Marshall ('03 and '04) has studied the oestrus cycle in the 

 sheep, and in the common ferret. He states that Scotch black- 

 faced ewes can, during the regular sexual season, ovulate without 

 pairing, as claimed by Bischoff ('44) for ewes in general, but 

 pairing, according to Marshall, even then may hasten the process 

 of ovulation, which outside of such rutting periods may be de- 

 pendent upon copulation. The common ferret, Marshall finds, 

 behaves as recent investigators have found to be the case with 

 the rabbit, ovulating only after pairing. The withholding of the 

 male greatly prolongs the period of heat, and in a few exceptional 

 cases is said to lead to the death of the female. 



Benecke ('79), Eimer ('79), Fries ('79). Van Beneden and Julin 

 ('80), and Van Beneden ('99) are all agreed that in all the various 

 species of bats that they have studied, pairing takes place several 

 weeks before the eggs leave the ovaries. 



The condition of affairs in mice has been disputed by Sobotta 

 ('95 and '07) and Kirkham ('07), who have claimed the inde- 



