628 
GlliBEltT E. JOHNSON. 
developed as those of the bisexual species, yet take no part 
ill the reproductive process or only “ re-£ertilise ” the females 
on rare occasions when the latter have exhausted the stock 
of spermatozoa produced in their genital organs. It would 
appear quite permissible to apply the term “female’^ to the 
reproductive individuals of the hermaphrodite species. They 
closely resemble the true females of the bisexual species of 
the same genera, the only essential anatomical difference 
being the presence of spermatozoa developed in the oviducts, 
which are hence called the “ seminal receptacles.” Indeed, 
there is evidence that the conversion of females into herma- 
phrodites is a process which is going on at the present day. 
In the parthenogenetic species the females do not develop 
spermatozoa, and males are entirely absent. 
So far as the question of its reproduction has received any 
attention at all, Rhabditis pellio appears to have been 
hitherto regarded as a purely bisexual form. But whether 
this is the case and whether the species is not somewhat 
variable in its sexual character are questions on which I hope 
the following investigation will throw some light. The males 
liave never at any time been seen tp take part in the repro- 
ductive process or even to exhibit any sexual instincts what- 
ever, nor are they numerically equal to the females, as in the 
bisexual species. 
When dead earthworms decay, the male and female nema- 
todes which develop from the larvae in the nephridia and 
coelom propagate i-eadily. But when larvae were removed 
from a freshly-killed worm and placed in an artificial 
medium, the proportion of productive adults was in most cases 
considerably smaller, the medium being for some reason less 
favourable to reproduction than the natural food. This must 
be borne in mind in considering the following cultural experi- 
ments : 
Culture A. — Two sexually mature females, which may or 
may not have been already fertilised by males, were removed 
from some decaying brown bodies of a Lumb. terrestris 
and isolated in worm-extract in watch-glasses. Both pro- 
