XII. 



AMPHIMIXIS OR THE ESSENTIAL 

 MEANING OF CONJUGATION AND 

 SEXUAL REPRODUCTION. 



Introduction. 



For more than a decade biological enquiry has been 

 engaged, with renewed energy, upon the problem of fertili- 

 zation. When the brothers Hertwig, and Fol had taught and 

 demonstrated the fusion of the nuclei of ovum and sperma- 

 tozoon, and had further shown that, before fertilization, the 

 egg undergoes certain preparatory changes resulting in the 

 extrusion of the previously well-known polar bodies,— an 

 attempt was made to understand the significance of these pro- 

 cesses. What can this substance be that it requires to be 

 thrown out from the ovum before fertilization ? The first 

 answer to this question depended on the then commonly 

 received, although never clearly formulated opinion, that ferti- 

 lization consisted in the union of two opposed forces, — of what 

 may be described as a male and a female principle which, 

 by their fusion, kindled anew that life which, without such 

 rejuvenescence, must gradually come to an end. Considering 

 the dominant theory as to the significance of fertilization, it was 

 certainly justifiable to endeavour to look upon these bodies, 

 expelled from the egg, as the bearers of one of the two antithe- 

 tical forces, which were previously united in a single ovum, but 

 which required to be separated in order to render the egg capable 

 of fertilization. The polar bodies were thus looked upon as 

 bearers of the male principle, by the removal of which the 

 ovum became for the first time sexually differentiated, i.e. 

 became female. This idea was not merely ingenious, it was 

 the legitimate result of those indefinite ideas as to the essential 

 nature of fertilization, which up to the present day have held 



