XII.] CONJUGATION AND SEXUAL REPRODUCTION. I97 



without such acceptance. Bunge ^ is certainly correct in main- 

 taining that we are not at present in a position to completely 

 explain any of the simple processes of life from known 

 chemical and physical forces ; but it by no means follows 

 that they are inexplicable by such means. All we can say 

 is, that everything that we do know about natural processes 

 tells against the rejuvenescence of life by conjugation believed 

 in by Maupas, as I have already pointed out in an earlier essay. 

 To my mind it is difficult to understand how an almost exhausted 

 vital force could be raised again to its original state of activity, 

 as the consequence of a union with another equally exhausted 

 force. Maupas can only reply that we do not understand the 

 essence of any ' phenomene primordial' ; but if we cannot follow 

 all the details of the chemical processes which for example 

 bring about the phenomena of assimilation, because they are 

 so extremely complex, and do not admit of our tracing the 

 changes which succeed each other through the rapidl}'' shifting 

 stages— because this is so, we do not therefore take refuge in the 

 assumption that the whole process is unintelligible. But this, 

 in my opinion, is the case with the 'rajeunissement karyoga- 

 mique ' of which we know neither the beginning — the exhausted , 

 condition of the vital force, nor the end — the rejuvenescence, 

 nor any intermediate stage. The whole conception is simply 

 a fancy, the outcome of earlier deeply rooted convictions as 

 to the necessity of death and the 'vitalizing' influence of fer- 

 tilization. I do not care, however, to base my opposition to 

 Maupas' views on the rejection, as fundamentally untenable, of 

 the theory of rejuvenescence ; the argument is superfluous. 



In considering how it is that amphimixis has come to be regarded 

 as a renewal or rejuvenescence of vital force ^ the question naturally 

 arises— why are we not content to see in this union of two nuclei, 

 that which observation shows to us, viz. the union of two nuclear 

 substances, and hence the mingling of two individually different 

 hereditary predispositions ? Maupas himself admits that this 

 occurs, and indeed allows that variability is favoured there- 

 by, thus supplying the necessary material for processes of 

 selection. Why are we not content with this explanation, why 

 do we seek for something further ? 



^ Gustav Bunge, ' Vitalismusund Mechanismus' ; ein Vortrag. Leipzig, 

 1886. 



