THE BEGINNINGS OF LIFE. 



selves capable, after one or several developmental stages, of 

 being converted into Planarics. There might possibly be a 

 reversion of the comparatively undifferentiated matter of the 

 ovum, after it had undergone certain unusual changes, into 

 an organism of a lower type ; but though such an outcome 

 from the egg of a Planaria might be, as it were, an occa- 

 sional and accidental occurrence, it could not on this account 

 alone be regarded as one of the regular stages in the Hfe- 

 history of Planarice. 



