190 



THE GENESIS OF SPECIES. 



[CHAP. 



Secondly, as regards the last-mentioned author's expla- 

 nation of such serial homology as exists in the centipede 

 and its allies, the very groundwork is open to objection. 

 Multiplication by spontaneous fission seems from some 

 recent researches to be much less frequent than has been 



AN ANNELID DIVIDING SPONTANEOUSLY. 



(A new head having been formed towards the hinder end of the "body of the parent.) 



supposed, and more evidence is required as to the fact of 

 the habitual propagation of any planariae in such fashion. 1 



1 Dr. Cobbold has informed the author that he has never observed a 

 planaria divide spontaneously, and he is sceptical as to that process taking 

 place at all. Dr. H. Charlton Bastian has also stated that, in spite of 

 much, observation, he has never seen the process in vorticella. 



