No. 2.] BLATTA AND DORYPHORA. 313 
to the longitudinal and also to the dorsoventral axis of the egg. 
The loops forming the equatorial plate are readily seen and 
counted. Ten in number, each probably attached to an 
achromatic fibril, they are arranged in such a manner that 
seven form a circle inclosing the remaining three. 
The divisions of these four products of the cleavage nucleus 
continue till about 60 to 80 cells have been formed, scattered 
irregularly through the granular ventral yolk. The axes of 
the spindles are inclined in various directions, and nothing in- 
dicates an early differentiation into cells destined on the one 
hand to remain in the yolk, and on the other to form the 
blastoderm. 
The numerous amceboid cells next migrate to the surface of the 
egg. In Fig. 25, representing the ventral third of a median cross- 
section, two of these cells have just reached the surface, while 
one is still on its way. On reaching the surface the cells first 
become sqmewhat conical, and then gradually flatten out. The 
tension of the cytoplasm is so great that the inclosed nucleus is 
forced to become lenticular (Fig. 26 a). The cells which have 
reached the surface, and are much scattered over the roof-shaped 
ventral face and the adjacent portions of the lateral faces, com- 
mence dividing tangentially, not by karyokinesis, as heretofore, 
but by akinesis. Figure 36 represents the lateral surface view, 
and Fig. 26 part of a transverse section of an egg in this stage. 
The division of the nuclei which have reached the surface is 
very rapid, and compact colonies of cells of different sizes and 
in different stages of the unequally constricting process charac- 
teristic of akinesis may be seen embedded in amceboid masses 
of protoplasm. I have given such a syncytium (enlarged from 
Fig. 36) in Fig. 34, and two of the dividing nuclei from other 
parts of the same egg in Fig. 35 4,c. The method of division 
is exactly like what was described above for the cells of the fol- 
licular epithelium (Fig. 5), omitting the peculiar nucleoli which 
I have not been able to detect in these nuclei. My observa- 
tions tend to show that all the future divisions in the formation 
of the blastoderm and those subsequently undergone by the 
serosa are akinetic, the densely coiled chromatin filament re- 
maining inert, and the division taking place by a constriction 
which often produces two daughter nuclei of very unequal size. 
I emphasize the fact that these forms of division could not have 
