244 THE EMBRYOLOGY OF THE HONEY BEE 



This rather remarkable condition does not appear in other 

 insects, and may be peculiar to the Hymenoptera. It recalls the 

 condition found by Madame Tschuproff-Heymons (1899) in the 

 Odonata and suggests that possibly the behavior of the yolk cells in 

 the Hymenoptera may have a phylogenetic significance, the epi- 

 thelium-like layer formed by the yolk cells at the periphery of 

 the yolk representing the vestiges of the ancient mid-intestine, 

 which undoubtedly was primitively formed by the yolk cells. If 

 this were the case however, similar conditions should be found 

 in the Orthoptera and other primitive orders. In Gryllus and 

 Gryllotalpa, according to Heymons (1895) the yolk cells form 

 an epithelial layer beneath the wall of the mid-intestine, but this 

 does not occur until shortly prior to hatching. In Dixippus, ac- 

 cording to Hammerschmidt (1910) the yolk cells form an epithe- 

 lial layer over the ventral surface of the yolk at a relatively early 

 stage. This layer Hammerschmidt regards as the "primary 

 entoderm", a view which is in harmony with the suggestion out- 

 lined above. 



