No. I.] CONTRIBUTION TO INSECT EMBRYOLOGY. 41 



I would here insert a few observations on gastrulation in 

 Stagmomantis Carolina, Gryllus luctuos^is, and CEcanthus 

 niveus. 



In Fig. 12 the ^^^ of Stagmomantis is represented in out- 

 line for the purpose of showing the relatively small size of the 

 germ-band which arises as in other forms from a thickening of 

 the blastoderm on the ventral face of the yolk. It is seen to 

 lie , somewhat nearer the broad posterior than the pointed 

 anterior pole. It is but slightly longer than broad, and its 

 wider anterior end, which is directed towards the upper pole 

 of the Q^^, foreshadows the procephalic lobes. Fig. 1 1 shows 

 that the germ-band of the Mantid, unlike that of Xiphidiiim, 

 is raised above the niveau of the yolk and has its marginal cells 

 sharply separated from the extra-embryonal blastoderm — or 

 serosa — as it is now called. This much flattened layer is, 

 nevertheless, encroaching on the edges of the germ-band to 

 form the amnio-serosal fold (ams.). At the anterior edge lies a 

 small cluster of cells {/>. o.) but little larger than those of the 

 germ-band. I believe that these may represent all that remains 

 of an indusium in Stagmomantis . 



The narrowly pear-shaped blastopore is very short. Sections 

 show it to be a deep groove, which like the median infolding 

 of other forms (Doryphora, Hydrophilns, Mtisca, etc.) is deep- 

 est posteriorly and grows shallower headward. As I failed to 

 find any of the stages immediately following the one figured, I 

 could not trace out the formation of the germ-layers. 



According to Bruce {'86, p. 17), who studied the same species 

 of StagjJiomantis , "When the union of the folds (of the amnion 

 and serosa) is effected and the embryo is separated from the sur- 

 face and covered ventrally by the amnion, the under layer is 

 formed, as in Mcloe and Thyridoptcryx as an ingrowth from the 

 median line of the embryo." This remark, together with his 

 Figs. XLII-XLIV, PI. IV, shows that he could not have ob- 

 served the formation of the layers from a groove and that he 

 must have based his inference on a stage later than the one I 

 have figured. 



In Gryllus luctuosus the blastopore is more like that of 

 Xiphidium. The outline of the egg is shown in Fig. 14. The 



