toith Report on Experiments. 
367 
Fig. 4. — Emhri/o of Strongyle 
kept in Soil for seventy 
hours. Length -^-^ of an inch^ 
with the embryos, and had caused the organic contents of the 
two larger vessels to decompose. However, some of the embryos 
within their envelopes were still alive. 
Another experiment consisted in placing several thousand 
embryos, still invested by their chorions, in water, which was 
allowed to evaporate before the fire. The increased warmth 
caused greater activity and hatching-out of the embryos ; but 
when the water had entirely evaporated and the worms had 
become dried-up, all attempts to restore their vitality failed. 
Effects of Soil on the Embryo. — On the 25th of October, a 
fresh examination was made both of the finely-sifted earth in 
the watch-glass and the coarse earth of other vessels, into which 
(after cleaning) I had placed a fresh 
supply of embryos. In each case 
plenty of living worms were de- 
tected, but they had undergone no 
change beyond a slight increase of 
length. After a lapse of seventy 
hours, neither mouth nor intestine 
had formed (Fig. 4). In some em- 
bryos the granules appeared to have 
increased, in others to have de- 
creased. So numerous were the living 
embryos, that in about two grains' 
weight of the soil I counted a dozen 
specimens. Later, on the 27th of 
October, and at various other times, 
I examined the soils both coarse and 
sifted, always finding living embryos 
that had undergone no structural 
changes. The earth was kept moist 
by occasionally adding a few drops 
of water. As long as the embryos remained in the moist soil, 
there was not even any attempt made by them to change their 
skins. At least, I never saw any evidence of moulting or 
ecdysis. In this fact it would appear that the embryo of the 
calf's lung-worm differs from that of the worm of the sheep. 
Professor Leuckart's experiments with the young of Strongylus 
filaria proved that the embryos, when kept in moist earth, 
underwent a change of skin within a period varying from 
eight to fourteen days. He administered some of these meta- 
morphosed embryos to young sheep, without, however, obtaining 
any positive results. It was clear that further changes of struc- 
ture in the larva? were necessary to ensure the success of feeding 
experiments. Without further insisting upon the fact of these 
differences of behaviour on the part of the embryos of the calf's 
