552 CLAEENCE E. McCLUNG 



clear cut description by Wilson of the failure of certain chromo- 

 somes to enter into synapsis is not an explanatory fact but an- 

 other 'subhypothesis.' Similarly, early separation of conju- 

 gants, delayed divisions of certain elements, the presence of 

 supernumeraries are merely so many condemnatory ' subhypoth- 

 esis.' The exact determination of the union of the character- 

 istic and well marked accessory chromosome, with a tetrad to 

 form a multiple is not a fact at all, not even a hypothesis, but 

 only a 'subhypothesis.' 



From this it is clear that Delia Valle, and others like him, 

 have set up in their minds the conception of an absolutely fixed 

 and invariable number of chromosomes of constant and un- 

 changing form as the hj^pothesis of chromosome individuality. 

 This is a man of straw, fathered by no biologist of standing or 

 character. His destruction in no way affects the existence of 

 the real image of a constancy in chromosome organization 

 consistent with our other knowledge of the living substance of 

 which these structures are a part. Such misinterpretation merely 

 condemns the judgment of the one who has no better discernment 

 of the real problem. It seems incredible that a biologist should 

 be capable of twisting the truth in such a way as to turn an in- 

 vestigator's meaning entirely around so as to make his results 

 support a converse. Only when his basic conception of chromo- 

 some constitution is fully appreciated does an explanation of 

 Delia Valle's attitude appear. This is expressed by him in sev- 

 eral places in some such terms as these: The chromosomes are 

 temporary and variable aggregates forming in the prophase and 

 disappearing in the telophase ('09). Between two mitoses the 

 chromosomes are so completely lost as individuals that finally 

 no trace of them can be found ('13). It is easy to see that, 

 with such a view of chromosome organization, no constancy is 

 possible and the quickest way to dispose of variable numbers is 

 to consider them the result of chance. 



But such a disposition of the case neglects certain objective 

 facts which can not be disposed of by consignment to the class 

 of 'subhypotheses.' It has long been known that the accessory 

 chromosome, and other heterochromosomes, preserve their mor- 



