136 BERTRAM G. SMITH 



in the uterus. In the third female (C) considered, in which all the 

 eggs were in the uterus, a second polar spindle was found in one 

 out of the three eggs sectioned. This result is sufficient to show 

 that sometimes, if not always, the second polar spindle is formed 

 while the egg is still in the uterus, previous to fertilization; 

 hence the penetration of the egg by the spermatozoon is not 

 required as a stimulus to the formation of the second polar spindle. 



The question arises whether the second polar spindle is normally 

 or ever present after the penetration of the egg by the spermato- 

 zoon ; in other words, do the processes of maturation and fertiliza- 

 tion overlap? We must first take into consideration the possi- 

 bility that eggs dissected from the uterus of a ripe female for pur- 

 poses of artificial fertilization may not be quite so far advanced as 

 eggs spawned and fertilized in a natural manner. Fortunately 

 it has been possible to check results obtained through artificial 

 fertilization by comparison with a case in which fertilization oc- 

 curred in a more natural manner. For the study of fertilization 

 three females, (C, D, and E), were principally used; eggs from the 

 gravid uteri of the first two were artificially fertilized in the usual 

 way; the third female spawned with a ripe male while the two 

 were being carried in a pail of water. 



Furthermore we must distinguish between what might be called 

 potential fertilization, the mere contact of the seminal fluid 

 with the gelatinous envelopes of the eggs, and actual fertilization, 

 the penetration of the egg proper by the spermatozoon. While 

 the act of fertilization is not consummated until the fusion of the 

 germ-nuclei, the influence of the spermatozoon is felt in many ways 

 as soon as it enters the egg cytoplasm, so that actual fertilization 

 may be said to begin as soon as the spermatozoon pierces the cell 

 wall of the egg. The time record is almost necessarily reckoned 

 from the moment of mixing of the two sexual elements, or poten- 

 tial fertilization; actual fertilization follows after an interval 

 necessary for the passage of the spermatozoon through the gela- 

 tinous envelope, which varies for the individual eggs and espe- 

 cially for eggs of different spawnings fertilized by different males, 

 and which can be determined only by a careful microscopical 

 examination of serial sections of each egg. 



