140 



BRISTLE-TAILS AND SPRING-TAILS. 



of Isotoma Walkerii, uuder the bark of trees. They are round, 

 transpai'ent. The development of the embryo of Isotoma in 

 general accords with tliat of the Phryganeidse and suggests on 

 embryological grounds the near relationship of the Thysanura 

 to the Neuroptera. 



The earliest stage observed was at the time of the appearance 

 of the primitive band (Fig. 164, a, b, folding of the primitive 



Development of a Poduran. 



band ; c, the dotted line crosses the primitive band, and terminates 

 in a large yolk granule) which surrounds the egg as in the Caddis 

 flies. Soon after, the primitive segments appear (Fig. 1G5; 1, 

 antennae ; 2, mandibles ; 3, raaxillaj ; the labium was not seen ; 5-7, 

 legs ; c, yolk sun'ounded by the primitive band) and seem to orig- 

 inate just as in the Caddis flies. Figure 166 is a front view of 



