EMBRYOLOGY OF CHRYSOPA, ETC. 139 



yolk as in Calopteryx, but more as in Aspidiotus, though it 

 rests more on the outside of the yolk than in those genera, 

 and the end of the abdomen rests on the outside of the yolk, 

 rather than rolled in Avithin the yolk ; but that the germ is 

 an endoblast (so far as that condition has any special signi- 

 ficance) is shown by the fact that the dorsal side of the 

 primitive band points inwards towards the centre of the 

 yolk, as in the Libellulidse, the Hemiptera, and a Coleop- 

 terous insect (Telephorus), in contradistinction to the Phry- 

 ganeidte and the Podurse (Isotoma), in which the germ or 

 primitive band floats entirely on the outside of the yolk. 

 After the procephalic lobes and rudiments of the appendages 

 of the head and thorax have begun to develop, a second 

 moult (visceral layer) of the blastoderm is made, Avhich 

 envelops the head and under side of the body much as in the 

 Libellulidse and Hemiptera. At this time the embryo is 

 much like that of the last-named insects. The germ does 

 not revolve in the egg, as in the Libellulidse, but the head 

 remains throughout embryonic life Jiext the micropyle. At 

 the next stage observed, the appendages of the limbs had 

 appeared, the embryo being situated on the outside of the 

 yolk, the end of the abdomen curved around on the opposite 

 side of the yolk. At this time the inner or " visceral layer," 

 forming a second moult of the blastoderm, envelops the germ, 

 much as in the Libellulidse, and Hemiptera, and Coleoptera 

 (Telephorus). It is evident that this faltcnhlatt of Weiss- 

 mann (or visceral layer of Brandt) is shed at a later stage 

 than the " amnion " proper. This stage corresponds Avith 

 that of Calopteryx figured by Brandt (pi. i, fig. 11). At 

 this time the germ of Diplax and Calopteryx (Libellulidoe) 

 floats within the yolk, but this difference I would regard as 

 having no special importance, as in the Hemiptera the germ 

 at the same stage of development rests on the outside of the 

 yolk in Corixa, while in the Pediculina, according to Melni- 

 kow's researches, the germ floats within the yolk, and Ave 

 shall see farther on that in the Curculionidse (Attelabus) the 

 germ rests on the outside of the yolk (ectoblast), Avhile that 

 of Telephorus is a decided endoblast, i.e. floats in the inte- 

 rior of the yolk. After this period, the embryo of Chrysopa 

 exactly corresponds to that of all the Libellulidse Avhose develop- 

 ment is knoAvn (Agrion, Calopteryx, Perithemis, and Diplax). 

 The embryogeny of Chrysopa is identical, then, Avith that 

 of the Libellulidse. What becomes, therefore, of the distinc- 

 tion between the " Pseudoneuroptera," and " true " Neuro- 

 ptera, insisted on by some of the leading entomologists, since 

 Erichson's day ? Never believing that the differences were 



