40 Mv. W. AVedekind on Alternation of 



goes on developing continually in a tachygenesis wliich 

 becomes constantly more and more accelerated. 



Moreover, up to the present it has nowhere been shown 

 that the retardation of ontogeny is only secondary. Fritz 

 ]\Iiiller, too, -who is much quoted to this end, certainly brings 

 forward in his well-known memoir many an instance of 

 tachygenesis, and also maintains that development is 

 frequently falsified by the struggle for existence which tlie 

 free-living larvse had to undergo; he remarks that this point 

 needs no further elucidation, since it is self-evident, &c., &c. 

 The author in question states that it is easy to understand 

 how even a direct course of development may again be trans- 

 formed through the struggle for existence into a development 

 with metamoi pilosis. But in no passage of his work does 

 Miiller adduce any fact whatever in favour of this assertion, 

 any more than the point has previously been proved by other 

 authors. To me, too, that nature in so many instances should 

 have made such a retrograde step is anytiiing but " self- 

 evident^^ and "easy to understand'^; and still less can I 

 ])icture to myself the inner causes oi such a process, especially 

 since I have long ago abandoned the pious belief of my 

 scientific childhood in the omnipotence of selection. 



The " utility " also of such a retarded development is 

 absolutely incomprehensible to me. For what have butterflies, 

 for instance, to gain from the fact that, with a more protracted 

 caterjjillar life, they are so much the longer exposed to the 

 danger of being devoured before they reach the final goal of 

 their development ? Or wherein are they benefited by 

 previously as caterpillars eating up the very plants upon 

 which they subsequently want to live as butterflies? 



And so probably in all cases the harmfulness of a slow 

 development can be demonstrated at least equally as well as 

 the advantage ; and even when the latter is really present, it 

 still need not on that account be an originating cause, but is, 

 as I interpret it, merely the external stimulus, which, in the 

 case of the s};ecies in question, has led to the longer ontogeny 

 persisting until the present day. 



In almost every instance, however, a species must derive 

 the greatest advantage from completing its developmental 

 stage as quickly as possible, in order afterwards to cuntinue 

 to live quite a long time as an adult animal. Among insects 

 I need only remind the reader of the highly organized 

 llymenoptera, of which the metamorphosis is no longer so 

 " complete '' as is that of the beetles, butterflies and moths, 

 &c. The metamoiphosis, e. g. in the case of the bees, which, 

 in contrast to that exhibited by the (.'tlan- orders referred to. 



