ci6 R- W. Hegner 



anterior end of the egg and the tail-fold extends a little more than 

 half-way up on the dorsal surface (Fig. 6). The tail-fold now 

 begins to recede as the embryo shortens and broadens (Fig. 7) 

 and in a short time coincides with the posterior end of the egg. 

 The embryo now grows laterally around the yolk (Fig. 8), its 

 various parts being situated approximately in the positions they 

 occupy at the end of about six days when it hatches as a larva. 



VI THE STRUCTURE OF THE EGG OF CALLIGRAPHA BIGSBYANA 

 AT THE TIME OF DEPOSITION 



At the time of laying the eggs of Calligrapha bigsbyana are not 

 always in the same stage of development, although usually polar 

 body formation is taking place. The egg figured (Fig. 9) was 

 fixed four hours after deposition. The polar bodies have already 

 been produced in this egg and the male and female nuclei are in 

 the act of conjugation. The egg consists of a large central mass 

 of yolk and a comparatively thin peripheral layer of cytoplasm, 

 the "Keimhautblastem" of Weismann. The interdeutoplasmic 

 spaces are filled with cytoplasm which is connected with the 

 "Keimhautblastem" by delicate strands of the same material. 

 The enormous amount of yolk contained in the eggs of these 

 insects makes the identification of other substances extremely 

 difficult. The yolk-globules range in size from large deutoplasmic 

 spheres to small granules, and, as the dissolution of some of them 

 is continually taking place, one is unable to determine where yolk 

 ends and cytoplasm begins. The only accumulations of cyto- 

 plasm large enough for examination are those surrounding the 

 nuclei within the volk mass, and the peripheral layer, the " Keim- 

 hautblastem." No differences in composition or staining qualities 

 were observed between the cytoplasm of these two regions. The 

 "Keimhautblastem" consists of a fluid ground substance in which 

 are suspended very fine granules. It is a homogeneous layer of 

 cytoplasm everywhere except at the posterior end of the egg. At 

 this point there is a disc-shaped mass of larger granules imbedded 

 within the inner portion of it. These granules stain deeply with 

 haematoxylin. They are easily seen not only in sections but also 



