No. 2.] BLATTA AND DORYVPHORA. 321 
the grayish yolk spheres, and very high powers are necessary to 
detect the delicate rays of the spindle or even the minute gran- 
ules of chromatin in the metakinetic and succeeding stages. 
The isochronism among all the nuclei in the different stages 
of development up to the formation of the blastoderm is quite 
as apparent as in Satta. Judging from the great number of 
eggs with resting nuclei and the very few eggs with kinetic 
figures, I conclude that division takes place very rapidly and is 
followed by comparatively long periods of quiescence. 
Fig. 61 represents one-half a cross-section through the equa- 
torial region of an egg containing a number of nuclei in its yolk. 
All the nuclei are resting and are surrounded by ameeboid 
masses of protoplasm. These cells often have the appearance 
of being in motion, most frequently in concentric paths. The 
nucleus is in the broader portion of the comet-shaped cell, 
which seems to be advancing head foremost. These cells are 
surrounded by numerous minute vacuoles that under the low 
power, with which Fig. 61 was drawn, appear like coarse granules. 
These cells divide rapidly and give rise to many smaller cells 
scattered through the whole yolk. A few enter the blastema 
layer and begin to proliferate rapidly. As soon as this mi- 
gration to the surface has taken place, the cells which have 
remained in the interior, and whzch do not go to the surface, stop 
dividing and take up positions at short but nearly equal distan- 
ces apart, through the whole yolk. Before assuming their defi- 
nite positions they have multiplied so rapidly that one may 
frequently see strings of three or four cells (Fig. 62 yz}). 
Often, too, in this stage most of the cells are in pairs, or, more 
accurately speaking, the egg contains many binucleate cells. 
The nuclei which have entered the surface layer of pro- 
toplasm divide tangentially. Sometimes the axis of the spindle 
is inclined at an angle less than go° to the radius of the circular 
cross-section, but in no case have I seen a spindle with its axis 
directed radially. The first divisions of the nuclei, which have 
entered the blastema, give rise to an even layer of cubical cells. 
By one more division of its constituent elements this blastema 
is converted into the blastoderm, which consists of smaller and 
more columnar cells. Sections taken in all directions through 
the egg show the blastoderm to be of even thickness over the 
whole surface (Fig. 63). 
