618 
GILBERT E. JOHNSON. 
fed on peptone are ahvays^oviparons. Those fed on putrefying 
worm are usually oviparous at first, but, since they produce 
a far larger stock of eggs than the peptone form, they 
become viviparous later, when the eggs are being discharged 
into the uterus faster than they can be laid. The embryos 
are ready to emerge before the eggs have been laid, and there- 
fore they hatch out in the uterus, and, when discharged 
from the parent’s body, are no longer enclosed in the egg- 
shell. The nematodes of the earthworm are thus oviparous or 
viviparous according to the nutritive quality of the food supply. 
But both the peptone form and the putrefaction form behave, 
so to speak, viviparously if they die before all their eggs are 
laid, for the fertilised eggs that remain in the uterus, being 
quite independent of the parent for their nourishment, continue 
their development, and the embryos hatch out within the 
uterus of the parent, in whose decaying body they thrive and 
Sfrow until nothin^' remains but a thin investment of cuticle. 
Identification. 
The encysted larvte from the coelom are reared to the adult 
stage (at which they can be identified) in the following 
manner. A number of the brown bodies from the tail of a 
freshly killed Lu mb. terrestris are placed in a watch-glass 
with a little water. Disintegration and decay set in very 
soon, providing a natural food medium for the nematodes 
Avhich emerge from the cysts. They grow rapidly, and within 
a week have developed into sexually mature adults of Rhab- 
ditis pellio, exactly, similar to those obtained from the 
worm decaying in its entirety (PI. 37, figs. 1 and 2). 
This, however, is merely a confirmation of the results 
obtained by the early investigators. The question which the 
literature of the subject does not appear to have hitherto 
answered is, whether the active larvie in the nephridia are 
the same species as these or not ? I have not discovered that 
any previous worker has ever removed the larvae from the 
nephridia and reared them to maturity in order to establish 
