CRITICISMS AND CONCLUSIONS. 49 



length of time required in the mouse according to our observations, 

 namely, from 4 to 15 hours, needs confirmation. 



According to the calculations of Tafani (18896, p. 114) the interval 

 between coitus and the penetration of the spermatozoon is 7 or 8 hours, 

 of Sobotta (1895, P- 6 3) an d Gerlach (1906, p. 8) 6 to 10 hours. Tafani 

 and Sobotta think the formation of the pronucleus requires only about 

 an hour from the time the spermatozoon penetrates the egg; whereas 

 Gerlach does not believe the pronucleus is formed so quickly. We have 

 already (p. 21) shown that the interval between coitus and penetration 

 may be much less, viz, 4 to 7 hours, and that the pronuclei probably 

 require only a few minutes for their development. 



D. OVULATION. 



It is desirable to know whether the time of ovulation has any fixed 

 relation to that of either coitus or parturition. 



All investigators except Gerlach (1906, p. 22) agree that in the 

 mouse ovulation is independent of coitus, although such is not the case 

 in some other mammals, e.g., the rabbit and the guinea-pig. 1 Regarding 

 the relation of ovulation to parturition, Kirkham (19076, p. 79) is the 

 only one, so far as we know, who makes any statement. He says that 

 ovulation takes place in from 1 to 2 hours after parturition; but as he 

 cites no authority for the statement and furnishes no evidence of his 

 own, one can not give his conclusion much weight. We have already 

 given evidence that it occurs at some time during a period extending 

 from 14^ to 28^ hours after parturition. 



There is some difference of opinion concerning the relation of the 

 time of ovulation to that of maturation, the chief cause of which seems 

 to us to be the failure to find any critical basis for distinguishing between 

 the first and the second maturation spindles. Tafani (1889, p. 22) says 

 ovulation occurs during the stage of the first spindle. While this, in 

 our opinion, is not true, the statement can be explained on the highly 

 probable assumption that he confused the first and second spindles. 

 Sobotta has changed his opinion since writing in 1895, and now (1907, 

 pp. 515, 519, 546; 1908, pp. 247, 250) believes that ovulation occurs only 

 during the monaster stage of the second spindle. He never finds the first 

 spindle in eggs encountered in the oviduct, but describes, as being found 

 in the oviduct (1907, p. 524, fig. 8), what he thinks may be a transition 

 stage between the first and the second spindles. Gerlach (1906, p. 14) 

 believes that the changes in the wall of the follicle that make ovulation 

 possible are not directly connected with the maturation changes within 

 the egg itself, and therefore that the rupture of the follicle may take 

 place at various phases of maturation ; but he says that at the earliest the 

 egg leaves the ovary in the stage corresponding with the beginning of 

 the first spindle, and at the latest in that of the second spindle; but this 



Cf. Kirkham, 19076, p. 79. 



