18 ROBERT H. BOWEN 
as in Hemiptera (Bowen, ’22 a, fig. 132). During the early 
development of the tail vesicles the central substance can be 
demonstrated with Fe-hematoxylin and it can be seen to retain 
its threadlike distribution even in the region of the vesicles. It 
would accordingly seem that the central substance cannot play 
the rdle in the development of the vesicles which the conditions 
in Hemiptera led me to suggest as a possibility (Bowen, ’22 b). 
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