76 CLA YPOLE. 



consider them the homologues of the second pair of Crustacean 

 antennae. 



In every way the apterygote insect appears to be truly primi- 

 tive ; no evidences of wings appear, and many points in shape of 

 eggs, cleavage, embryonic membranes, and appendages show 

 resemblances to the lower Arthropoda. One question has been 

 purposely left untouched in this brief review : that of gastrula- 

 tion. It is only from studies based on sections that safe con- 

 clusions can be drawn, and the difficulties introduced by the 

 method of germ-layer formation described for Anurida render 

 further facts necessary concerning these processes in other 

 forms before general principles can be safely deduced. 



Wellesley College, 



Wellesley, Mass. 



