The Development of the Wings of a Caddis-fly Platyphylax designatus Walk. 585 



dorsally on the wall of the cavity, hanging down from the upper part 

 (Text figure V). The free edge of the rudiment is either pointed in a 

 ventral direction of towards the peripodial pore ; in the former instance 

 the cavity is more flattened and the rudiment lies niore or less parallel 

 to the cuticular layer. In the last cited text figure (V) two rather 

 extreme cases are given and of these the figure to the left is, at this 

 stage of development, the more exceptional. In a series through a 

 rudiment at this stage one can find, by going over all the sections, 

 that the free edge of the rudiment changes its position; it may at some 

 place be found pointed more directly towards the peripodial pore, 

 in other sections be more ventrally directed. 



Rcay- 



P memo. 



Text figure V. 

 Sections through a wing nidiment showing difference in position of the rudiment within the peri- 

 podial cavity. Dorsal above. cu, cuticula; V.cav, peripodial cavity; P.memb, peripodial membrane. 



x280. 



Attention has been called to the fact that the rudiment now shows 

 in surface view, that the niargins are quite different; the more anteri- 

 orly faced one is concave and the more posterior one convex. The 

 curved line forming the anterior cavity is not equally curved throughout, 

 the greatest curvature being one-third the distance from the more 

 ventral end of the rudiment. The posterior margin of the rudiment 

 is more regulär than the anterior, and, as development goes on, a 

 greater change is noticed in the latter (Text figure VI). In the re- 

 lative positions of the two rudiments it is clearly seen that the one 

 on the mesothorax lies with its longitudinal axis nearer the similar 

 axis of the body thän does the metathoracic rudiment. The concavity 



