No. I.] CONTRIBUTION TO INSECT EMBRYOLOGY. 7 1 



this process are stripped back over, and finally drawn into the 

 yolk, where they undergo dissolution when the body walls have 

 met in the median dorsal line. The defects in Ayers' descrip- 

 tion of CEcantlms ('84) were pointed out at p. 43. 



Gryllotalpa, the only other Gryllid, which has been studied, 

 seems to differ considerably from Grylhis and (EcantJms. Ex- 

 amination of Korotneff' s figures ('85) shows that this difference 

 is probably more apparent than real. In his surface views, 

 there is a wide gap between his Fig. 2, representing the egg in 

 a preblastodermic stage, and his Fig. 3, representing quite an 

 advanced embryo. One is thus left without any guide to the 

 exact relation of the just-established germ-band to the yolk- 

 surfaces. Korotneff' s defective account of the formation of 

 the germ-layers would seem to show that he did not study these 

 early stages closely. It is obvious that Gryllotalpa is blasto- 

 kinetic both from Korotneff' s statement that the embryo 

 moves during revolution and from his figures 5, 7, and 8, but 

 the exact nature of the process is not clear. The possibility 

 of the embryo's passing to the opposite surface of the ^g% is 

 not precluded by the conditions seen in Figs. 7 and 8. Judg- 

 ing from Gryllus and CEcanthiis I am inclined to think that the 

 embryo exhibits both ana- and katatrepsis, but that Korotneff 

 has overlooked the former and misinterpreted the latter 



movement. 



In the Locustid^, as represented by Xiphidimn and Orcheli- 

 imnn, we find a modification of the blastokinetic process ob- 

 served in Grylhis. Instead, however, of arising near the caudal 

 pole, the germ-band is formed on the middle of the ventral 

 surface, and instead of passing around the caudal pole during 

 anatrepsis it passes through the yolk as if to reach the dorsal 

 surface by a shorter path. Katatrepsis is essentially the same 

 as in the Gryllidse, the embryo passing around the caudal pole. 

 This lack of coincidence in the anatreptic and katatreptic paths 

 is one of the most striking peculiarities of Locustid develop- 

 ment; since it is known to occur in no other insect. It is 

 probable that the anatreptic embryo originally passed around 

 the lower pole, but that owing to the formation of the embryo 

 higher up on the ventral surface, and perhaps also to an acqui- 



