SEX DETERMINATION IN THE WHITE-FLY 291 
mosomes observed in one sex may have a different value from 
those observed in the other. 
The maturation phenomena in the lower Crustacea have not 
as yet been fully cleared up, although a good deal of work has 
been done here. However, it seems to be a general rule that 
parthenogenetic eggs which give rise to parthenogenetic females 
form only one polar body with no reduction of chromosomes. An 
exception to this rule was discovered by Brauer (94) in a small 
proportion of the parthenogenetic eggs of Artemia salina. There 
two polar bodies were given off and reduction took place, but the 
second polar body then rejoined the nucleus and restored the 
diploid number. In the course of later investigations, Fries (’09) 
did not confirm Brauer in this respect and is inclined to doubt 
it, while Petrunkewitsch (’02) regards the phenomenon as path- 
ological. It is interesting to note in this connection that Artom 
(11) has since found that there are two distinct races of Artemia 
salina in Italy, one of which is always sexual, while the other 
can develop parthenogenetically. The former has eggs which 
give off two polar bodies and undergo reduction, while the latter 
form only one polar body with no accompanying reduction. It 
may be that contradictory results obtained by previous inves- 
tigators are due to the fact that they were working on similar 
different races. If crosses could be made between the two races, 
some light might be thrown on this problem. The fact remains 
in any case that the diploid complex is retained in some way or 
other in parthenogenetic eggs which give rise to another parthe- 
nogenetic generation. 
Sexual eggs give off two polar bodies and reduction occurs. 
The question of how parthenogenetic sexual eggs which give rise 
to females (if there really be such) differ from those which give 
rise to males is not known. From the fact that reduced eggs 
must be fertilized in order to develop, and that reduction is 
known to occur in the spermatogenesis of closely related species, 
it seems likely that the male is not haploid. The male-producing 
eggs probably extrude certain chromosomes, as do those of Aphids 
and Phylloxera, and in the spermatogenesis there is perhaps a 
JOURNAL OF MORPHOLOGY, VOL. 34, NO. 2 
