No. 2.] BLATTA AND DORYPHORA. 315 
etal nuclei show the two highly refractive nucleoli of the 
surface cells; when treated with alcohol only, both the surface 
and yolk nuclei exhibit the same closely wound, deeply stainable 
chromatin filament. Such exact similarity in size, shape, and 
minute structure is very strong evidence in favor of community 
of origin. Still I have not been able to find an egg without 
nuclei in the yolk, notwithstanding I sectioned many eggs in 
the blastoderm stage. I am inclined to think that such a stage 
may not occur, but that the last of the cleavage nucleus 
products go to the surface simultaneously with the passage in 
the opposite direction of the first blastoderm products. Thus 
the enucleate yolk stage would be slurred over. 
The time required for the development so far described is 
approximately as follows: The first polar spindle is formed in the 
ovaries ; the second polar spindle during oviposition. Both polar 
globules have been constricted off by about the sixth hour from 
the commencement of oviposition. By the end of the first day 
the female pronucleus has fused with the male pronucleus, and 
the cleavage nucleus thus formed has reached the back of the 
granular ventral yolk. The products of the cleavage nucleus 
are formed and reach the surface by the end of the third 
day. By the end of the fourth day the blastema is completed. 
During the fifth day the blastema nuclei proliferate and 
complete the blastoderm by the close of the sixth day. The 
development is, of course, accelerated by a rise and retarded by 
a fall in temperature, though not to the extent observed in 
many other animals. 
Before passing over to a description of the early stages of 
the egg of Doryphora, I will recapitulate the movements of the 
nuclei by means of diagrams of a longitudinal and equatorial 
cross-section of the egg (Figs. 39 and 40). In these diagrams 
a is the cephalic, 6 the caudal end, ¢ the ventral, d the dorsal, 0 
the lateral surface. The shaded body / is the homogeneous 
yolk, the dotted portions y the granular yolk. The germinal 
vesicle starting from the central point e goes to the surface, 
describing the path represented by the line ef Here it gives 
off by two successive divisions the two polar globules /! 
and f%, and then as the female pronucleus turns back to 
go in the opposite direction. The line representing the pas- 
sage of the germinal vesicle to the surface is really too long, 
