374 
GENETICS: A. M. BANT A 
nounced characteristics contrasting with those of a male on these several 
points. In other words maleness and femaleness are generally assumed to 
indicate definite and precise alternative and opposing states only one of 
which may obtain in the same individual organism. 
With unisexual forms known deviations from the supposed mutually exclu- 
sive conditions of maleness and femaleness were until recently confined to a 
comparatively few cases of hermaphroditism and gynandromorphism. Such 
cases have been defined as sex mosaics — definite gonads or portions of the 
gonads or other parts of the body being described as distinctly of one or of the 
other sex. 
However, there are at least three known cases of the common occurrence 
of unmistakable intermediate sex forms — sex intergrades. These are Riddle's 
hybrid pigeons, 1 Goldschmidt's hybrid gypsy moths 2 and the writer's Cladocera 
material. These are not sex mosaics but sex intergrades. 3 That is to say, 
they are not fully male fri certain definite portions of the body and fully fe- 
male in other portions but frequently as a whole and (in the writer's ma- 
terial) almost always in certain parts they clearly possess both femaleness 
and maleness — they are as a whole and by parts distinctly intermediate as 
regards sex. 
In the Cladocera material there sometimes occurs an individual which 
might very readily be considered a sex mosaic, inasmuch as its complement 
of secondary sex characters consists of some apparently fully male and some 
fully female characters. But the majority of these secondary sex characters 
are obviously intermediate between the fully female and the fully male char- 
acter, and there are comparatively few of the sex intergrades which do not 
have one or more such intermediate sex characters. These intergrading 
sex characters clearly indicate that we have to do not with sex-mosaics but 
with sex intergrades. 
In Cladocera the population ordinarily consists entirely of females and re- 
production is by means of parthenogenetically developing eggs. Occasion- 
ally males appear and some females produce the less usual type of egg which 
must be fertilized in order to develop. This occasional sexual reproduction 
has given rise to the notion that there is an innate sexual cycle in these 
forms. 
In all the many lines of the writer's stock however, previous to the appear- 
ance of the sex intergrade strains, males were seen only two or three times and 
in as many lines. 4 Though no sexual reproduction has occurred in any case 
the various lines continue to reproduce with their original vigor. Hence as 
applied to this material the supposed innate sexual cycle seems quite an 
unwarranted assumption. 
In the writer's stock previous to the appearance of the recognized sex in- 
tergrade strains there were a few individuals of one strain of Daphnia longi- 
spina which may have been sex intergrades. These individuals failed to re- 
produce but it is probable that they were really sex intergrades and that 
