ON THE NEMATODES OF THE COMMON EAl! THAVORM. 645 
Those, too, which find their way in by the spermiducal aper- 
tures and travel up the vasa deferentia are tlie same as are 
found on opening the seminal vesicles. 
(ii) Secondly, those which enter by the dorsal pores and 
the oviducal apertures find themselves in the coelomic cavity. 
Here they are attacked as foreign bodies by the amoeboytes 
and encyst. Keng (8, p. 391) describes the way in which 
the amoebocytes surround and cover nematodes in the coelom, 
hampering their movements by means of fine protoplasmic 
threads into which they can become drawn out. He gives a 
drawing' (pi. v, fig. 44) of a nematode struggling with amoe- 
bocytes. When the nematode is completely covered it 
apparently sheds the outer layer of its cuticle. The ainoebo- 
cytes soon die and turn brown. The cyst is composed of the 
loosened outer layer of cuticle with its investment of dead 
brown amoebocytes. The completely and partially encysted 
nematodes are gradually worked backwards through successive 
segments by the movements of the worm until they reach the 
tail, where, with cysts of Monocystis and discarded sette, 
they are compacted by pressure into the flattened oval masses 
and cemented together by their investment of broken-down 
coelomic corpuscles. The great majority of tlie nematodes 
found in the coelomic cavity of a fresh-killed worm are 
encysted. But in addition to these there are some which are 
covered with amoebocytes but not completely enclosed by a 
cyst, and some which are quite free. Those that are found 
quite free have probably not yet been attacked by amoebo- 
cytes. Those that ai’e covered with amoebocytes but are not 
fully encysted were probably about to become so when the 
worm was killed. The latter, being only slightly encumbered, 
are no doubt those which, disengaging themselves from the 
imprisoning lymph-cells, are the first to be seen escaping 
from the brown bodies. The only occasion that I know 
when the larvae emerge from their cysts is on the death and 
decay of the worm, when the food supply becomes plentiful and 
nutritious. But only a certain proportion of the fully encysted 
larvae do so. The remainder appear to have degenerated, for 
