44 GEORGE T. HARGITT 



The evidence obtained from coelenterate eggs would not 

 permit one to dissent from this view. In the absence of contrary- 

 evidence in this group, the evidence from other groups would 

 lead me to agree that there is no reason to believe the coelen- 

 terates differ in this regard. 



Recently Robertson ('16), McClung ('17), and others have 

 expressed a more radical view. Robertson believes the chro- 

 mosomes are 'individually indentical' in succeeding genera- 

 tions and 'persist as entities' from one cell division to another. 

 McClung is likewise convinced that each chromsome persists as ' 

 a distinct structure; during interkinesis the chromosome may 

 extend its boundaries and diffuse its substance, but each body 

 retains just as precise a limit (though it is usually unrecognizable) 

 during this period as it does during its stay in the usual form. 

 This is a return to the older view of a distinct morphological in- 

 dividuality which Wilson and others have abandoned. McClung 

 says of the chromosomes, ''either they actually persist as dis- 

 crete units of extremely variable form, or they are entirely 

 lost as individual entities and are reconstituted by some ex- 

 trinsic agency." It is quite unwarranted to state that extrinsic 

 agencies are all that can explain a reintegration of chromosomes 

 under these conditions. McClung gives us a very valuable 

 critique of chromosome individuality, and, in his chief argu- 

 ments, makes use of analogies between chromosomes and other 

 organic behavior. The restitution of the normal form in re- 

 generation and the production of a typical adult form by 

 developing eggs are due to internal organization and not to 

 'some extrinsic agency.' On the same basis, the restitution of 

 chromosome form is scarcely to be ascribed to external agen- 

 cies, even if there have been a loss of identity in interkinesis. 

 McClung contrasts organization with lack of organization in 

 urging a persistent and continuous individuality, but organiza- 

 tion does not involve preformation, as his discussion assumes. 



In discussing chromosomal relationships Payne ('16) says: 

 "It seems to me it is time we were realizing that evolution of 

 chromosomes as morphological units, in chromosome numbers, 

 and in chromosome behavior has been as diverse as it has been in 



