ON THE NEiLATODES OE THE COMMON EAliTHWOKM. 643 
it is not difficult to understand how it g’ets there. When 
the cocoon is being* slipped forward towards the head of the 
worm it must pass over the nephridiopores, and it is quite 
easy to imagine a few nematodes escaping from thenephridia 
into the cocoon through these apertures. 
(5) Occasions when the L arval Ne m a tod e attain s 
Sexual Maturity. — The sexually mature adult of Rhab- 
ditis pellio is found engaged in reproduction in large 
numbers in the dead earthworm decaying in soil, as is shown 
in the case of worms which have died a natural death in the 
earth and are found there in a state of puti’efaction, as well 
as by ai-tificial methods. But I have never seen the adult or 
its eggs or newly hatched larvEein the live earthworm, and I 
do not believe that they ever occur there. 
Thinking that Rh. pellio might possibly attain the mature 
condition in the soil as well as in the dead worm, I have 
searched samples of earth for it. But I have failed to find it. 
It is not, therefore, certain whether the larval Rh. pellio 
in the course of its development becomes sexually mature in 
ordinary soil or only in the dead worm. But if a larva 
which has passed out into the soil from the bodv of a live 
worm finds a quantity of nutritive substance such as the 
decaying carcase of some animal, it seems reasonable to 
suppose that under such circumstances it will mature and 
reproduce just as it would have done had it remained in the 
worm till the latter died. Such behaviour would correspond 
to that of the larvae of the free-living soil-inhabiting species, 
which grow into adults and propagate when they find some 
putrefying substance in the soil. 
(6) Mode of Infection of a Fresh Worm by the 
Larval Nematode. — From the fact that the adult nematode 
is entirely absent from the live earthworm it is evident that 
the infection of a fresh worm is carried out by the larva. 
There are two possible ways of entrance into the body : 
(i) through the external apertures of the coelomic cavity, 
or (ii) by the mouth or anus into the gut and through the 
gut-wall. 
