VIII.] 



HOMOLOGIES. 



183 



researches to be much less frequent than lias been sup- 

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

 habitual propagation of any planariae in this fashion.* But 

 even if this were as asserted, nevertheless it fails to explain 



AN ANNELID DIVTDTNO BPONTANEOUSLT. 



(A new head having been formed toward the hinder end of the body of the parent) 



the peculiar condition presented by Syllis and some other 

 annelids, where a new head is formed at intervals in certain 

 segments of the body. Here there is eWdently an innate 



• Dr, Cobboid has informed the author that he has never observed 

 a planaria divide ppontancoiisl}', and he is skeptical as to that process 

 taking place at all. Dr. II, Charlton IJastian has also stated that, in spilo 

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



