580 
GENETICS: A. M. BANTA 
(7) and (8) outline and armature of the lateral post-abdomen margins^ 
in the female these margins are decidedly concave and bear posteriorly 
no teeth or only rudimentary 'teeth.' In the male the margin is 
slightly or not at all concave and bears larger teeth which also extend 
posteriorly much farther than in the female. Since the two post- 
abdominal margins often differ in character the nature of each margin 
constitutes a diagnostic sex character. 
That these eight characters are really diagnostic secondary sex char- 
acters for the female is indicated by the fact that they occur in all 
individuals in the lines of Simocephalus which are reproducing par- 
thenogenetically in the usual fashion, i.e., producing nothing but fe- 
males. Again in a derived strain, in which for a time there appeared 
both females and males, but no sex intergrades, each female and male 
possessed all the secondary sex characters indicated above for its sex. 
The sex intergrades are of almost all possible sorts from females 
with a single male secondary character to females with all eight of the 
secondary characters male, hermaphrodites with many combinations of 
secondary sex characters, and, finally males with one to several (never 
as many as eight, however) female characters. 
The highly male-like female intergrades produce few young. Not 
infrequently they are entirely sterile. A female intergrade with as 
many as six strong male secondary characters rarely produces young. 
Many female intergrades with fewer than six male secondary sex char- 
acters are likewise sterile. In most of the sterile individuals eggs are 
produced but either they fail to develop after passing into the brood 
pouch or, more generally, the ovarian development is not completed 
and the eggs disintegrate in the ovary. To cite illustrative cases: two 
female intergrades in the 132d generation each had five male charac- 
ters and though eggs began to form, the ovarian development was not 
completed and no eggs ever appeared in the brood pouch. A sibling 
of these had only the antennae male in character yet produced only a 
single brood. This case however is rather unusual as such individuals 
are usually quite prolific. In the 133d generation a female intergrade 
with four male secondary characters produced three broods consisting 
in all of only 15 individuals. On the other hand some individuals with 
several secondary male characters prove to be very prolific. A sibling 
of the last-mentioned individual had five secondary male characters 
and in addition one side of its post-abdomen was somewhat male in 
character yet it had a high prolificacy. In general in addition to being 
more prolific one may say that female intergrades with few o less 
distinctly male characters produce a smaller percentage of males and 
