C48 
GILBERT E. .TOHNSOX. 
of a further generation. The young reach the same stage of 
growth as that of the nephridial larvae. They then leave the 
carcase of the worm and wander into the soil. Here they live 
for a longer or shorter period but do not increase in size. 
Sooner or later they infect an earthworm, making their way 
in by the external apertures of the coelom. Those that enter 
by the nephridiopores take up their position in the terminal, 
bladderdike part of tlie nephridia. Those that use the spermi- 
ducal apertures travel up the vasa deferentia and occupy the 
seminal vesicles. Lastly, those that pass in by the dorsal 
pores and the oviducal apertures find themselves in the coelom, 
Avhere, being attacked by the amoebocytes, they encyst. These 
encysted larvae coated with amoebocytes are worked back- 
Avards by the movements of the Avorm till they come to rest 
in the tail end of the Avorm, Avhere, together with other foreign 
bodies, such as cysts of Monocystis and discarded setae, and 
AAdth masses of dead broAvn-coloured amoebocytes, they are 
compi’essed and cemented into the brown bodies Avhich are 
found there. 
In this larv'al condition the nematodes remain during a 
protracted period Avithout growth, the encysted form Avithout 
movement, until on the death and decay of the Avorm in the 
soil they grow, mature and reproduce. 
When infested Avorms are eaten by moles, thrushes or other 
predatory animals, it is probable that the nematodes ti’avel 
doAvn the alimentary canal, and, Avhether alive or dead, pass 
out Avith the faeces into the soil. I have not yet any evidence 
of the existence of an alternate host, within whose body the 
nematode spends a part of its life-history. 
During its larval existence the active nephridial form 
probably passes out and in by the external apertures of the 
coelom and spends longer or shorter periods in the soil. Or 
it may change hosts, entering and inhabiting another Avorm. 
But if, while in the soil, it finds some animal or vegetable 
substance in putrefaction, it may mature and reproduce on 
the spot, as it Avould have done in the Avorrn had it remained 
till tlie death of the latter. 
