47 



correlation with the increase in ths size and efficiency of the compound 

 eyes. The long scape in Synlestes is to be attributed to hypertrophy ; 

 our larvae exhibit a scape of intermediate length, which may be 

 accepted as indicating the ancestral form. The length and narrowness 

 of the gills is also an interesting point, since it shows us that Austro- 

 lestes cingulatus, Burm, generally regarded as the most archaic 

 .iiember of the genus, still possesses gills closest in form to those 

 found on the fossil larvse. 



