152 WHEELER. 



EXPLANATION OF PLATE IL 



(Figs, ri and 12, Stagmomantis Carolina; Figs. 13 and 14, Gryllus lucttiosus ; 



Figs. 15-20, Xiphidiiim ensiferum.) 



Fig. II. Surface view of gastrula of Stagmo77iaiitis. X 150. />.o., rudiment 

 of indusium.''; i>/., blastopore; ams., amnioserosal fold extending just over the 

 edge of the oval germ-band. 



Fig. 12. Outline of egg of Stagmomantis showing the position and relative 

 size of the germ-band during gastrulation. 



Fig. 13. Surface view of gastrula of Crj//«j. X 150. ^wj-., amnioserosal fold 

 extending just over the edge of the germ-band ; bl., deeper posterior end of blasto- 

 pore. 



Fig. 14. Outline of egg of Gryllus showing the relative size and position of 

 the germ-band during gastrulation. 



Fig. 15. Surface view of a Xiphidiuni embryo during the closure of the 

 amnioserosal fold over the mouth. Eight segments in the trunk, p.o., indusium ; 

 ;/., pale area between the indusium and the head ; pel., procephalic lobe ; ams., 

 edge of amnioserosal fold, o., stomodsum ; md.s., mandibular segment ; mx.s?-, 

 first maxillary segment ; n.g., neural groove ; s., serosal nuclei ; a.s.,"^ first abdom- 

 inal segment. 



Fig. 16. Surface view of head during the separation of the indusium. Stage 

 of Fig. 3 (C), Plate I more highly magnified, p.o., indusium ; nn., shrunken nuclei 

 of the indusium ; s., serosal nucleus ; z., pedicel connecting the indusium with the 

 head ; pel., procephalic lobe ; lb., labrum ; 0., stomodasum ; at., antenna ; tc.s., 

 tritocerebral segment ; 7nd.s., mandibular segment ; 7nx.s.,^ first maxillary segment. 



Fig. 17. Median transverse section through the indusium while still a simple 

 thickening of the blastoderm (serosa). X 230. s., serosa ; p.o., portion of indu- 

 sium with normal nuclei ; ««.,' shrunken nuclei ; 7171.^ less shrunken nuclei ; d., 

 thickened periphery of the organ ; v., yolk. 



Fig. 18. Median transverse section of the indusium while the amnioserosal 

 fold is closing over the disk. X 230. Letters as in Fig. 17. 



Fig. 19. Median transverse section through the indusium after the complete 

 closure of the amnioserosal folds. X 230. a/71.,'^ outer indusial layer ; p.o., inner 

 indusial layer ; ««.,' shrunken nuclei. 



Fig. 20. Median transverse section through the indusium just after it has 

 begun to spread. X 230. Letters as in the preceding figures. 



