22 Gro. W. TANNREUTHER 
? 
parthenogenetically only one polar body is formed; in those which 
required fertilization, two polar bodies were formed and that in — 
insects in general the polar bodies are not thrown off, but that the 
chromatin mass remains in a vesicle in the protoplasm of the egg 
near the periphery and are often called polar nuclei. 
PETRUNKEWITSCH, 1902, in studying Apes found that the eggs 
deposited by the queen in drone cells never showed any signs of 
being fertilized. Two polar bodies are always formed. The first 
polar body always divides with a reduction, half being thrown out 
of the egg, and the half retained united with the second polar body 
and formed a “Richtungscopulationskern” with the normal number 
of chromosomes. This nucleus by three consecutive divisions gives 
rise to eight cells with double nuclei which ultimately become the 
testis of the adult drone. 
Parthenogenetic eggs from eight different species of aphids 
were studied for the purpose of comparing the formation and be- 
havior of the polar, body. In every instance only one polar body 
was formed and the chromosomes showed no indication of the 
formation of a second. The polar body disappears by breaking up 
into fine granules within the cytoplasm near the periphery of the 
egg. There is no reduction division in the formation of the polar 
body. The chromatin behaves as in ordinary cell division. An 
attempt to explain what stimulates the pronucleus to further deve- 
lopment would be purely hypothetical. | 
b) Sexual generation. 
The reproductive organs of the sexual aphids are similar to 
those of the parthenogenetic. Pl. 50, Fig. 29, represents the con- 
dition of a single follicle in a half-grown embryo. Each follicle is 
divided into an end ligament, end chamber or ovariole and oviduct. 
The end ligament is a continuation of the distal end of the follicle 
which tapers down to a capillary calibre and is attached to the 
dorsal wall of the embryo. The end chamber, often called ovariole 
or in some instances ovary, is the most important or prominent 
portion in the embryonic development of the reproductive organs. 
It originates from a cluster of primitive germ cells, which become 
separated from the completely formed blastoderm where it first 
begins to invaginate. The more external cells of this group forms 
an epithelial membrane which becomes the follicular epithelium of 
the adult follicle. The epithelial cells placed more distally pro- 
