605 



ARTnTTK Wir-LKY. 



of invagination iiarrowino; down to a small pore which persists 

 as the aniniotie {)ore. ]\Iy views, however, dilVer from those of 

 TIevmons, in that I regard the ventral llexnre as primary, 

 while Heymons regards the dorsal llexnre of yonng embryos of 

 Cliilopoda and IVnlnrida^ as primary, and he thinks that this 

 dorsal llexnre has been lost by the embryo of Lepisma. 

 Knowing what takes place in the embryos of V. nov;xj-bri- 

 tanniai, I am qnitc satisfied that the early ventral ilexnre 

 of the Chilognatha (Diplopoda) is primitive, and that the 

 provisional dorsal flexure of the embryos of Cliilopoda and 

 Podnridai is a transitory, ccnogenctic, intercalated phase of 

 development. 



The ventral flexure of the embryo of Lepisma is therefore to 

 be ri>garded as comparable with the primitive ventral flexure 

 which occurs in Chilognatha and in l*eri[)atus (see below). 



Heymons says (4, p. (520) : — " Sncht man bei luihercn 

 Inseeten uach einen\ Anklang an die ansgesprochen ventrale 

 Kriimmung von Lepisma, so ist dieser wohl zweifellos in der 

 von mir Caudalkriimmung genannten Umbiegunar des hintereu 



Fig. G.— Sagittal section through embryo of Lepisma saecharina, to 

 sliow ventral flexure, amniotic cnvity, and amniotic pore. Mesoderm and 

 yolk omitted, a. Amnion, r. Amniotic cavity. //. Head end of en\l)ryo. 

 /). Amniotic pore, .v. Serosa. L Tail end of embryo. (Simplilicd alter 

 Heymons.) 



Korperendes vieler Insecteuembryoneu gegebcn. Dieselbe 

 zeigt sich bei den Orthoptereu, den Odonaten, Ephemeriden 



