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EDMUND B. WILSON 
ters and the more obvious internal features are concerned. Taken 
by itself this case may seem to form a legitimate piece of evidence 
against Boveri's theory. It cannot, however, be taken alone, but 
must be viewed from the more general standpoint given by the 
evidence as a whole. We are still too ignorant of the significance 
of the ^'sex-chromosomes'' to form an adequate opinion as to the 
meaning of the Y-element. It may be in this case (as I earlier 
suggested) a degenerating element, or may represent an excess of 
a chromatin that is duplicated elsewhere in the chromosome- 
group; but these and other speculative possibilites that suggest 
themselves may well await the outcome of further study. 
Department of Zoology, Columbia University, December 23, 1909. 
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