No. I.] CONTRIBUTION TO INSECT EMBRYOLOGY. 29 



eye is distinctly marked out and its cells are arranging them- 

 selves to form the ommatidia, as is evident from the regular 

 series of pale dots. The labrum, now considerably enlarged, 

 is spade-shaped in ventral aspect. The antennae have grown 

 in length, and the saltatory legs (/a) are assuming their defin- 

 itive characters. The large tapering pleuropodia stand out 

 prominently on the first abdominal segment. Near the bases 

 of the legs the thoracic stigmata are distinctly seen. They 

 had made their appearance in Stage G, but for obvious reasons 

 could not be shown in the figure. 



The anterior end of the embryo continues to move up the 

 ventral surface of the ^^Z-i straightening out as it rises. 

 Finally the flexed terminal segments of the abdomen are 

 again bent back to their original position in line with the 

 rest of the body. Since their flexure these segments (the 8th- 

 iith) have been the only portion of the body provided with a 

 completed dorsal wall {vide Fig. 7). After the bending back 

 of the abdominal tip its segments still retain a certain inde- 

 pendence and make no attempt to embrace the yolk of the 

 posterior pole as do the segments in front of them. It is for 

 this reason that the abdomen presents a constriction just in 

 front of the eighth segment. This constriction is especially 

 noticeable in profile view. 



The turning of the lower pole of the ^^^ seems to take place 

 very rapidly compared with other equally important processes 

 of development, such as the passage of the embryo through 

 the yolk. I infer this from the relative scarcity of embryos in 

 the act of returning to the ventral surface. I have, however, 

 succeeded in finding all the stages in the process of revolution, 

 and feel quite as confident of having correctly interpreted my 

 preparations as if I had studied the living &gg. 



6. The Stages Intervening between Revolution and 



Hatching. 



Fig. 9 represents an embryo that has just straightened out 

 on the ventral surface of the yolk, which the reader may 

 imagine as extending up beyond the head to nearly twice the 



