50 THE MATURATION OF THE EGG OF THE MOUSE. 



statement is based on his assumption that oviducal eggs without polar 

 cells contain the first spindle, a view which arises from his being unable 

 to distinguish between the two spindles in the monaster stage. This 

 statement of Gerlach's has been disproved by Sobotta. 



Lams et Doorme (1907, p. 284) maintain that ovulation takes place 

 only during the stage of the second spindle; but, as Sobotta (1908, 

 p. 259) points out, they contradict themselves by describing as a first 

 maturation spindle one found in an ovum occupying the oviduct. Ac- 

 cording to Kirkham, the first polar cell is always formed in the ovary; 

 but, as we have seen, this statement is supported, in part at least, by 

 false evidence. In spite of some diversity of opinion regarding the pre- 

 cise state of the egg at ovulation, all agree that ovulation occurs during 

 the stage of the second spindle. We, too, find this to be generally but 

 not invariably true. It is probably owing to the unusually large number 

 of eggs in the earlier stages of maturation studied by us that we have 

 found in the periovarial space eggs in the stage of the first spindle, and 

 also in the oviduct others that have already formed the first polar cell 

 but have not yet developed the second spindle. It might be maintained 

 that these eggs had been abnormally retarded in their development, 

 and it must be admitted that such cases are not numerous enough to 

 allow one to say that it is a common condition. On the other hand, 

 nothing else about these eggs pointed to their being in any way abnormal, 

 and no signs of degeneration were discoverable. These cases seem, 

 therefore, simply to prove that the general rule regarding the time of 

 ovulation in relation to maturation is not so inflexible as one w T ould 

 infer from the observations hitherto published. 



E. SIZE OF EGG. 



Sobotta and Kirkham alone have published measurements of the 

 egg, Sobotta on fixed material and Kirkham on living material. Sobotta 

 (1908) states that ovarian eggs before the formation of the first polar 

 cell measure from 65 to 70 micra in diameter, and oviducal eggs 60 micra; 

 but he does not say what is the average in the former case, nor that the 

 latter measurement is an average, though such is presumably the case. 

 Gerlach thinks there is considerable individual variation, and Lams et 

 Doorme hold that oviducal eggs are smaller than ovarian ones. Our 

 conclusions (see table 2, p. 14, also p. 24) substantially confirm the above, 

 except that the averages we give are a little less than the dimensions 

 published by Sobotta. Kirkham (19076, p. 72) arrives at a different con- 

 clusion, namely, 80 micra as the diameter of ovarian eggs and 73 to 78 

 micra of oviducal eggs; but there may be some doubt concerning the 

 reliability of his measurements because his methods may have been 

 somewhat faulty, as we shall explain directly. Tafani, who was the first 

 to study living eggs, carefully states (1889, p. 6) that he collected them 

 from the oviduct and kept them at the proper temperature in the fluid 



