142 WHEELER. [Vol. VIII. 



penetrated as far as but not into the yolk. They are then 

 washed in water, dehydrated and mounted in balsam. The 

 sexual ducts together with their ampullae may be distinctly 

 traced on the yellow background of the yolk and structures 

 which lie just beneath the integument, like theoenocyte clusters 

 and the nerve-cord, may be more readily studied than in 

 specimens prepared by Methods I and II. The figures on 

 Plate V and Fig. lo, Plate I were drawn from such partially 

 stained embryos. 



The methods here described give good results, not only with 

 XipJiidimn and Blatta, but also with all the other insects and 

 crustaceans which I have examined. 



The outlines of the figures in the plates were drawn with 

 an Abb6 camera. 



Clark University, 



Worcester, Mass., May loth, 1892. 



