GENETICS: A. M. BANTA 
581 
sex intergrades than those having a larger number or more definitely 
male characters. 
Males that bear one or more female secondary sex characters in 
nearly every case have incompletely developed reproductive systems — 
one or both testes, though filled with sperm, being shorter than normal 
or lacking all or part of the sperm duct. In most cases the entire sperm 
duct is lacking. Some males, normal in their secondary sex characters, 
have similar incomplete reproductive systems. 
By propagating from female intergrades we are able to continue the 
production of mixed broods — females, males and sex intergrades. 
This has now continued for 16 generations with no apparent change in 
the ratio of the various sex forms and with no apparent tendency of the 
stock to lose vigor or become less prolific. 
From the sex intergrade stock we have derived in its third genera- 
tion (the 133d generation under laboratory conditions) a normal strain 
producing nothing but typical females. 
The origin of this all-female-producing strain is of interest. An 
almost sterile hermaphroditic intergrade produced only two young. 
One of these offspring was a female intergrade. This individual pro- 
duced 202 young, 2 of which were normal females, 16 were female in- 
tergrades, 4 were hermaphrodites, 12 were male intergrades and 67 
were normal males. In addition 3 individuals were not examined 
while 10 females (including female intergrades) and 88 males (includ- 
ing male intergrades) were undescribed. Probably only two indi- 
viduals (1% of the whole), from the entire number of ofifspring from 
this individual were normal females. The only sibling of this female 
intergrade was a normal female which produced nothing but typical 
females, and from this individual came a derived normal strain which 
has now descended for 23 generations in the usual fashion without re- 
version to the production of sex intergrades. For two generations, 
however (the 13th and 14th from its origin from the sex intergrade 
strain), this derived strain did produce a considerable percentage of 
males. These males were all normal however and their sisters were 
all normal females, there being no return to the production of sex inter- 
grades as in the parent stock. Following these two generations, in 
which males were produced, this derived strain has produced nothing 
but normal femxales in the nine generations which have occurred to 
date (August 10). From the 11th generation of the sex intergrade 
strain a second normal strain producing only typical females has been 
derived. More recently two additional normal all-female-producing 
strains have appeared. 
