364 ROBERT S. MCEWEN. 



directly with this factor. Unfortunately Cole gives no record 

 of temperature. Nevertheless, so far as data on this point go, 

 it seems improbable that his work was done at a sufficiently 

 higher temperature to account for the difference in results. In 

 this connection another feature of Cole's work which makes for 

 some uncertainty is the fact that the records for his flies just 

 cited apparently refer to only 50 per cent, of the insects tested. 

 What the other 50 per cent, did might possibly be significant, 

 at least as regards comparative records for the wild type. Lastly, 

 perhaps the most pertinent point to be indicated is this. One 

 conceivable explanation for the poor showing of Cole's vestigial 

 animals in the unlined tube is the fact that presumably they 

 were not previously selected for their ability to crawl on glass, 

 as was the case to a certain extent with those used by the writer. 

 It seems clear, however, that neither this, nor any of the other 

 points mentioned, account at all for the fact that whereas Cole's 

 results showed the vestigials, when given a proper footing, nearly 

 or quite the equals of his winged flies, in the present experiments 

 the wild type completely outclasses the vestigials under all 

 conditions, even when correction has been made for use of 

 wings by the former and slipping by the latter. 



