IV.] FOUNDATION OF A THEORY OF HEREDITY. 229 



have been retained up to the present day unless it possessed 

 some very important physiological significance. We may 

 safely maintain that it would have disappeared long ago if 

 it had been without any physiological importance. Relying 

 on our knowledge of the slow and gradual, although certain, 

 disappearance, in the course of phylogeny, of organs which 

 have lost their functions, and of processes which have become 

 meaningless, we are compelled to regard the process of the 

 formation of polar bodies as of high physiological importance. 

 But this view does not exclude the possibility that the process 

 possessed a morphological meaning also, and I believe that we 

 are quite justified in attempting (as Butschli^ has recently 

 done) to discover what this morphological meaning may have 

 been. 



Should it be finally proved that the expulsion of polar bodies 

 is nothing more than the removal of histogenetic nucleoplasm 

 from the germ-cell, the opinion (which is so intimately con- 

 nected with the theory of the continuity of the germ-plasm) 

 that a re-transformation of specialised idioplasm into germ- 

 plasm cannot occur, would be still further confirmed ; for we 

 do not find that any part of an organism is thrown away 

 simply because it is useless : organs that have lost their 

 functions are re-absorbed, and their material is thiis employed 

 to assist in building up the organism. 



III. On the Nature of Parthenogenesis. 



It is well known that the formation of polar bodies has been 

 repeatedly connected with the sexuality of germ-cells, and that 

 it has been emplo3'ed to explain the phenomena of partheno- 

 genesis. I may now, perhaps, be allowed to develope the 

 views as to the nature of parthenogenesis at which I have 

 arrived under the influence of my explanation of polar bodies. 



The theory of parthenogenesis adopted by Minot and Balfour 

 is distinguished by its simplicity and clearness, among all other 

 interpretations which had been hitherto offered. Indeed, their 

 explanation follows naturally and almost as a matter of course, 

 if the assumption made by these observers be correct, that the 



^ Biitschli, ' Gedanken iiber die morphologische Bedeutung der so- 

 genannten Richtungskorperchen,' Biolog. Centralblatt, Bd. VI. p. 5, 

 1884. 



