186 CRITICISMS ON " THE ORIGIN OF SPECIES " 



" The fundamental conception of this hypothesis is, that, under 

 the influence of a general law of development, the germs of organisms 

 produce others different from themselves. This might happen (1) 

 by the fecundated ova passing, in the course of their development, 

 under particular circumstances, into higher forms ; (2) by the 

 primitive and later organisms producing other organisms without 

 fecundation, out of germs or eggs (Parthenogenesis)." 



In favour of this hypothesis, Professor Kolliker adduces 

 the well - known facts of Agamogenesis, or " alternate 

 generation " ; the extreme dissimilarity of the males and 

 females of many animals ; and of the males, females, and 

 neuters of those insects which live in colonies : and he 

 defines its relations to the Darwinian theory as follows : 



" It is obvious that my hypothesis is apparently very similar to 

 Darwin's, inasmuch as I also consider that the various forms of 

 animals have proceeded directly from one another. My hypothesis 

 of the creation of organisms by heterogeneous generation, however, 

 is distinguished very essentially from Darwin's by the entire absence 

 of the principle of useful variations and their natural selection : 

 and my fundamental conception is this, that a great plan of de- 

 velopment lies at the foundation of the origin of the whole organid 

 world, impelling the simpler forms to more and more complex 

 developments. How this law operates, what influences determine 

 the development of the eggs and germs, and impel them to assume 

 constantly new forms, I naturally cannot pretend to say ; but I 

 can at least adduce the great analogy of the alternation of genera- 

 tions. If a Bipinnaria, a Brachialaria, a Plutcus, is competent to 

 produce the Echinoderm, which is so widely different from it ; if 

 a hydroid polype can produce the higher Medusa ; if the vermiform 

 Trematode ' nurse ' can develop within itself the very unlike Cercaria, 

 it will not appear impossible that the egg, or ciliated embryo, of a 

 sponge, for once, under special conditions, might become a hydroid 

 polype, or the embryo of a Medusa, an Echinoderm." 



It is obvious, from these extracts, that Professor Kollikcr's 

 hypothesis is based upon the supposed existence of a close 

 analogy between the phenomena of Agamogenesis and the 

 production of new species from pre-existing ones. But is the 

 analogy a real one ? We think that it is not, and, by the 

 hypothesis, cannot be. 



For what are the phenomena of Agamogenesis, stated 

 generally ? An impregnated egg develops into an asexual 

 form, A ; this gives rise, ascxually, to a second form or 

 forms, B, more or less different from A. B may multiply 

 asexually again ; in the simpler cases, however, it does 



