314 JORDAN. [Vol. VIII. 



to the fact that in the newt's Q,^g only a slight quantity of pig- 

 ment attends the path of the sperm, but chiefly to tne absence 

 of any essential divergence in structure between the two pro- 

 nuclei- It occasionally happens that one may pick out from 

 the rest a pronucleus which is perceptibly larger or is sur- 

 rounded by a greater quantity of protoplasm than the others, 

 and I have naturally been inclined to regard such a body as the 

 female element. This, it will be recognized, is a very inadequate 

 basis for such identification, and careful examination of all the 

 joronuclei found in an egg has served only to convince me more 

 strongly of the unsatisfactory nature of such a criterion. 



The union of the two pronuclei takes place ordinarily about 

 six to eight hours after the ^gg is laid. The place of meeting 

 does not seem to be constant or predetermined. It is never in 

 the geometric center of the &gg, but is nearer the upper pole, 

 and is usually, so far as I have been able to determine, in the 

 neighborhood of the position occupied by the germinal vesicle 

 before dissolution. The general phenomena attending the 

 union of the pronuclei are substantially such as described by 

 Hertwig ('77). The pronuclei that I have figured in Fig. 23A 

 present a typical appearance. The inner one (/) may perhaps 

 be regarded as more probably the female since it is surrounded 

 by the larger quantity of protoplasmic substance, and since the 

 other (in) has apparently just impinged upon it from the side. 

 Such identification, however, is based on pure analogy and on 

 no sure recognition-marks. The question here arises as to 

 whether the female pronucleus exercises any power of selection 

 from among the several suitors at her disposal or whether it is 

 a mere matter of proximity that determines which male 

 nucleus shall unite with the female. I may here state, what 

 to some will doubtless seem superfluous, that I have never 

 seen any evidence whatever that more than one male element 

 unites with the female. Why the one individual so favored 

 should be preferred above his fellows is somewhat problematical. 

 It is obvious, however, that other things, such as proximity, 

 etc., being equal, the sperm first entering would have the 

 advantage. Its earlier maturation would bring about a recip- 

 rocal movement of both male and female which would soon 



