198 AMPHIMIXIS OR ESSENTIAL MEANING OF [Xlf. 



Obviously for no other reason but that we are saturated 

 with the old notion that the egg cannot develope without fer- 

 tilization, that fertilization is the same as vitaHzation. But was 

 not this view overthrown long ago by facts ? Are we not aware 

 that, under certain circumstances, the &gg can develope without 

 fertilization ? And is not this often true, for example in the 

 Bee and in Apus^ of that very ^g<g which is also capable of 

 fertilization? No one would have regarded fertilization as 

 the vitalizing of the &%% if the great majority of ova had 

 developed parthenogenetically, or if science had first become 

 acquainted with parthenogenesis and, later on, with fertilization. 

 We should then have said that there must be some advantage 

 in the mingling of two hereditary tendencies which has led to 

 the introduction of amphimixis. But the facts are otherwise, — 

 for centuries mankind has recognized this mingling as the indis- 

 pensable antecedent to the development of offspring, and 

 now, when we find that, under certain circumstances, an ^gg 

 can develope without fertihzation, we are unable to get rid of 

 the old prejudice in favour of the view that the mingling 

 is something more than a mere preliminary to develop- 

 ment,— that it is an accessory force which bears some special 

 and entirely peculiar significance. We cling to some supposed 

 after-effect of the vitalizing influence of fertihzation, ex- 

 tending through many generations, and against such an 

 illogical theory even facts fight in vain, for the number of 

 generations through which this after-effect is supposed to ex- 

 tend, is entirely dependent on the will of the controversialist, 

 and keeps pace with the increasing length of the observed series 

 of parthenogenetic generations. Maupas himself finds the num- 

 ber of 'such generations, which may succeed each other in some 

 ' rare ' species of Crustacea and Insecta, entirely insufficient to 

 justify the conclusion that these agamic generations can con- 

 tinue indefinitely. I certainly believe that in most cases they 

 are not of unlimited duration, because nature has chiefly fitted 

 them for a cj^clical method of reproduction, — for a regular 

 alternation of parthenogenetic with sexual increase. But there 

 are species like Cypris reptans which I have investigated (see 

 Part II of this essay), in which it is certain that no such cycle 

 exists, and that parthenogenesis continues without interruption. 

 I have observed about forty generations in the case of Cypris 



