in CRITICISMS ON " THE ORIGIN OF SPECIES " 95 



tion, 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 development lies at the foundation of the 

 origin of the whole organic 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 generations. If 

 a Bipinnaria, a Brachiolnria, a Pluteus, 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 Pro- 

 fessor Kolliker's hypothesis is based upon the 

 supposed existence of a close analogy between the 

 phsenomena 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 phaenomena of Agamogenesis, 

 stated generally ? An impregnated egg develops 

 into a sexless form, A ; this gives rise, non-sexually, 

 to a second form or forms, B, more or less different 

 from A. B may multiply non-sexually again ; in 

 the simpler cases, however, it does not, but, acquir- 

 ing sexual characters, produces impregnated eggs 

 from whence A, once more, arises. 



