288 FRANZ SCHRADER 
To sum up, the eggs of all Orthoptera are subjected to reduc- 
tion. Those which are parthenogenetically developed give rise 
to females, while those which are fertilized result in a mixture of 
sexes. How, then, is the chromosome number kept constant, 
and why, since a reduced egg has only one sex chromosome, 
is not a male developed from such eggs? As indicated in case 
of the tick, this question might find a satisfactory answer in the 
assumption that the spermatozoon affects the formation or be- 
havior of the polar bodies, such that its entrance into the egg 
causes the second polar body to be cast out or disintegrate, sex 
being then dependent on the kind of spermatozoon which has 
entered. We might then assume that in eggs that are not fer- 
tilized, the second polar body fails to be extruded or, if formed, it 
rejoins the nucleus. In the former case, there would be a hap- 
loid complex of dyads, each of which breaks up into the compo- 
nent units at a later stage, while in the last-named case, the dip- 
loid number is immediately restored by the rejoining second 
polar body. 
Parthenogenesis is also known in the Lepidoptera, and in this 
connection the Bombycidae and Liparis dispar might be specially 
mentioned. Platner (’88) thinks that two polar bodies are 
given off by parthenogenetic eggs of the latter, but unfortunately 
he was unable to rear offspring from these to the stage where 
sex can be determined, and previous experiments with the same 
species admit of no definite conclusion. Although cytological 
work on parthenogenesis has been followed out to only a very 
limited extent, some very interesting observations have been 
made on the maturation phenomena in hybrids, which seem to 
offer the most convincing evidence thus far produced of the 
occurrence of two equation divisions in maturation. Federley 
(713), in his well-known crosses of Pygaera species, found that no 
synapsis takes place prior to maturation and, from both cyto- 
logical observations as well as the fact that after two maturation 
divisions the number of chromosomes is still practically equal to 
the sum of the haploid numbers of the parents, concludes that 
two equation divisions must occur. The evidence given by Fed- 
