172 Schrader. 
by a single cell layer of the normal blastoderm cells, which have been 
undergoing rapid division since reaching their position at the edge of 
the egg. 
The two types of cells can be distinguished without any difficulty. 
The cleavage cells, as well as the blastoderm cells to which they give 
rise, are less than one half as large as the giant cells which take their 
origin in the polar nucleus. During the division phases, the blastoderm 
cells show ten chromosomes without exception, whereas the giant cells 
typically contain thirty or more chromosomes. In the resting stages, 
the former are characterized by one or two nucleoli, while the giant 
cells contain five or even more. Finally, no blastoderm cells seem to 
be situated among the giant cells, so that when the single cell layer 
is complete around the periphery of the egg, it comprises two distinct 
areas, one of blastoderm, and one of giant cells (Fig. 19 and 27). The 
presence of these giant cells at the blastoderm stage has already been 
noted (SCHRADER, 1922) in a previous paper; but although the possi- 
bility of their derivation from the polar bodies was mentioned, it was 
at that time regarded as so unlikely that it received very little 
consideration. 
It is of interest to note that such irregularities as occur in the 
giant cells, occasionally take place at a later period in the yolk cells 
also. Possibly some of these last named cells may at times join the 
giant cells, but there is no evidence that such association would be 
anything but accidental. 
Later History of the Giant Cells. 
The normal blastoderm cells now begin’ to encroach on the area 
occupied by the giant cells, pushing in from all sides. As if actual 
pressure were exerted on them, the giant cells heap up and, as a con- 
sequence, are then found as an irregular mound of cells at the peri- 
phery (Fig. 20 and 28). Finally the advancing blastoderm nuclei, 
continueing their encroachment, push underneath the mass of giant 
cells, and crowd them entirely away from the periphery. This com- 
pletes the blastoderm proper, and a single layer of cells, each endowed 
with ten chromosomes, now invests the periphery. The mass of giant 
cells, remaining close to their former site, are characterized as before 
by a multiple number of chromosomes and nucleoli. But although 
divisions are few, growth does not keep pace with them and as a result 
the size of the cells becomes comparatively smaller. In the blastoderm 
