ON THE NEMATODES OE THE COMMON EARTHWOEM. 639 
Maupas also ( 10 , p. 623) has only once succeeded in finding 
Rh. pellioin the soil. 
(2) A Period of Independent Existence passed 
in the Soil after the Death and Decay of the 
Earthworm underground. — A Dumb, terrestris was 
killed and allowed to decay. When the nematodes which it 
contained had become sexually mature and begun to repro- 
duce, the worm was transferred to a fairly shallow glass dish, 
four inches in diameter, filled with soil which had previously 
been heated to kill off any nematodes present in it. The 
decaying worm was coiled up in as small a space as possible 
and placed in the centre of the fioor of the dish. The earth 
was spread around and over it to a depth of about one inch 
and then moistened. Water was afterwards added from 
time to time in order to keep the earth sufficiently moist to 
prevent the desiccation of the nematodes. About two weeks 
after the experiment was begun, the soil in all parts of the 
dish was found to be teeming’ with nematodes. The worm 
occupied only a small space below the sui’face of the soil in 
the centre of the dish. But as far away as almost at the very 
edge of the soil, where it tended to become dried np, the 
nematodes were plentiful. Careful examination indicated 
that their relative abundance in different jiarts of the soil in 
the dish was no longer determined by the desire to be near 
to the dead worm foi’ the sake of the food afforded by its 
])utrefying body. 
Although there were probably some thousands of nema- 
todes in the soil, not a single adult was seen away from the 
worm. All those that had wandered away into the 
surrounding soil were larvm, offspring of the adults intro- 
duced with the worm, and had reached the same stage of 
giowth as that of the larvae found in the nephridia. Six 
months later they were alive and plentiful but had not grown. 
Shortly afterwards the earth was accidentally allowed to di’y 
and almost all of them died. But as much as eight months 
later, i. e. fourteen months after the beginning of the 
experiment, one larva was still alive and had not grown any 
