80 Psyche [Juiie 



comes closely applied to the serosa, except at the two poles, and 

 remains intact until the hatching of the nymph; the inner indu- 

 sium (Figs. 8-9, ind. 2) joins to the amnion near the head of the 

 embryo and takes on the usual functions of the serosa during the 

 revolution of the embryo. Between the fifth and sixth day the 

 amnion (and the inner indusium) breaks open near the head of 

 the embryo and the re^'olution commences. The head of the em- 

 bryo leaves the amniotic cavity and moves upward to the dorsal 

 side of the egg, towards the original ])osition of the primitive 

 streak; but when the head is well round to the dorsal side, the 

 entire embryo, including the amnion and inner indusium, begins 

 to revolve round the longitudinal axis of the egg, the revolution 

 from the amniotic cavity continuing at the same time (Fig. 9) 

 until the embryo lies on the ventral side of the egg in the normal 

 ])osition of insects during the later stages of embryonic develop- 

 ment. 



An embryonic cuticle covers the embryo, entirely sheathiiig all 

 its members; a thickening of the cephalic portion of this cuticle 

 forms the "egg-burster." Thus the mature embryo is enveloped in 

 three coverings, apart from the chorion, viz. : The serosa (Fig. 

 10s), forming the outermost covering, the outer indusium (Fig. 

 10, ind^.) and the "embrj'onic cuticle" (Fig. 10, cw). The latter is 

 generally referred to as the amnion, but there is little probability 

 of the amnion having anything to do with its origin. In fact we 

 question whether the amnion enters into the final membrane 

 enveloi^ing the adult embryo of Hemiptera (and perhaps all 

 insects). The growth of the amnion over the ventral surface of 

 the embryo has not been demonstrated; and the onl^^ other way 

 for it to envelope the embryo would be by "substitution" (by 

 disintegration and reformation over the surface of the embryo). 



The Development of the Trophi. 



A comparison of the development of the embryonic head of 

 Siplianta to that of Pristhesancus^ demonstrates that they are 

 fundamentally identical and that the differences that arise are 

 due to the secondary developments of the head-capsule and its 

 relative position to the thorax. 



iMuir, F. and J. C. Kershaw. On the later embryological stages of the head of Pristhesancus 

 papuensis. Psyche, Vol. 18, No. 2, (1911). 



