1886, | Entomology. 461 
the entoderm and digestive canal. The cells of the primary ento- 
derm (the yolk cells) undergo a radial division of the yolk, the 
' yolk-pyramids thus arising melting into each other centrally. 
Some of the cells grow and form, under the serous membrane 
which has not yet disappeared, the dorsal wall of the body, and 
the dorsal plate or dorsal organ. Through the growth of the 
parts forming the lateral walls of the body, the dorsal organ 
gradually becomes covered, its cells sink into the yolk and seem 
to break into fragments. After the ectodermal parts of the diges- | 
tive canal (fore and hind intestine) have formed, amceboid cells 
still migrate into the yolk, and seem to contribute to its fluidity 
(verflussigung). After hatching, the whole yolk by a pumping 
movement, gradually becomes, including whatever is contained in 
the same, partly degenerate cells, thus pushing the so-called pri- 
mary entoderm into the portion of the fore-intestine, called the 
crop. The mesenteron receives no epithelial covering from the 
Primary entoderm, and the epithelium of the mid-intestine, 
almost everywhere between the yolk and mesoderm; the heart 
becomes indicated in the form of two furrows, which draw near. 
_ blood-lacuna which covers the dorsal side of the yolk and be- 
comes reduced to the cavity of the heart. 
EXPLANATION OF PLATES XVIII AND XIX, 
LETTERING, 
abc, amceboid blastodermic cells, dpm, dorsal diaphragm, 
ani, antenna. en, endodermal cells. 
ar, arterial sinus, ent, enteric layer. 
i blastoderm cells. J, fat-body. 
< blastoderm, g, ventral ganglion. - 
» abdominal vesicles. H, At, heart. 
Z, lacuna. 
4? , cavity of the myoblast. 
m; mouth, 
