32 



WHEELER. [Vol. VIII. 



and has the distinctly yellow tint of old chitin. Its outer sur- 

 face is minutely papillate. On the appendages the cuticle is 

 much thinner than it is on the trunk and though it stains it 

 does not show a differentiation into three layers. 



Before shedding the first cuticle the hypodermis secretes a 

 second larval skin which persists till after hatching. 



In Fig. IV, I have attempted to represent semi-diagrammatic- 

 ally the condition of the envelopes at a time when the eyes 

 be^in to acquire pigment. The chorion (<:/^.) is much distended 

 and the egg larger and more resistent to the touch then it was 

 during the autumn. Passing from without inward we first 

 meet with the cuticle secreted by the serosa {sr. c). Then 

 follows the serosa itself {sr) to the inner face of which the 

 remains of the outer indusium {ind.^) are applied. At the ex- 

 treme anterior end of the ^^^ both these cellular envelopes 

 appear to be much thickened and pass into a cylindrical pedicel 

 of granular plasma which I shall call the columella (<?/.). This in 

 turn is continuous with a conical mass of cells (ind.-), the re- 

 mains of the inner indusium which was stripped from the head 

 in a preceding stage. Its cells, as shown in the figure, are in an 

 advanced stage of disintegration. The cytoplasm of the different 

 elements is reduced to a mass of granules and the chromosomes 

 have become agglomerated into little spheres floating in the 

 clear nuclear plasma. The process of degeneration is similar to 

 that which I have described as occurring in the "dorsal organ" 

 of Blatta. Between the mass of degenerating cells and the 

 head of the embryo lies a granular coagulum {am. s). This I 

 take to be the amniotic serum which is forced up into 

 the anterior pole by the enlarging of the embryo and the 

 consequent decrease in the space between the body walls and 

 the chorion. The columella and the remains of the inner indu- 

 sium are held together and thus temporarily prevented from 

 complete disintegration by the thick cuticle of the latter. 

 This cuticle still envelops the embryo and extends forward to 

 the anterior pole where it seems to be attached to the inner face 

 of the outer indusium. Passing further inward we next 

 meet with the first larval cuticle (Iv. c^), which has been shed, 

 and the second larval cuticle {Iv. c~), which is still in organic 



