1909. ] THREAL- YORMS OF THE RED GROUSE. 343: 
for a longer period, and allowing the sediment to settle. The 
sediment is then, with as little water as possible, taken up 
by a pipette and placed in the test-tube of a centrifugal machine. 
After a few minutes’ rapid rotation the heavy matter which 
accumulates at the closed end of the test-tube is removed and 
examined microscopically. The very first time we tried this 
method we succeeded in showing that heather is, so to speak, 
“crawling” with thread-worms, amongst which we thought we 
recognised the larvee of 7’. pergracilis. We also found aphides, a 
dipterous larva, thousands of pollen-grains, tardigrades, thysanura, 
rotifers, nematodes, vegetable débris, desmids, beetle-larvee, 
young hemiptera. One of the nematodes had striated cuticle 
and was about the proportions of 7. pergracilis; some of the 
others were relatively much longer and seemed to be free-living. 
Amongst the nematodes was a male with the characteristic 
spicules of the 7. pergracilis, of the same sort of outline 
and in the same relative position. The tail was curved and 
showed as yét no genital bursa. The mouth led into a short 
cesophagus (| ) with a small swelling. The body contained a. 
eranular substance. 
These eggs and larve must exist in quite countless millions, 
every dropping must contain many thousands; roughly speaking, 
a grouse—at any rate during the night—relieves itself about once 
an hour, and the droppings occur every few yards on the moors. 
Hence the occurrence of Trichostrongylus pergracilis even in 
grouse chicks of a tender age is readily explained. 
One must not forget that a grouse-dropping consists of two 
parts: (1) the excreta from the intestine, which contains the tape- 
worm and 7'richosoma eggs; and (2) the more fluid contents of the 
ceca, Which alone contains the Vrichostrongylus eggs and larve. 
This excretion usually forms a cap upon the firmer dejecta from 
the intestine, but sometimes occurs alone ; it either case it probably 
is washed away by the first rain or quickly dries up, whilst the 
more solid excreta will retain their shape for a couple of years 
before disintegrating, as is shown by finding them unchanged in 
shape but with charred ends on moors that were burnt some two 
years ago. 
We have seen that a young grouse-chick, not more than ten 
days old, contains in its ceca segmenting ova, young larve, and 
adult males and females, and we are faced with the old problem 
as to whether the egg preceded the fowl or the fowl the egg. 
Are the segmenting ova we find in these young ceca of the same 
generation as the larvee and adults, or are they the offspring of 
the adults¢ On the whole, I incline to the second alternative. 
I think most probably that the larvee, either coiled up in the ege- 
shell or free, obtain access to the alimentary canal with the food 
or water, make their way to the ceca, and there, remote from the 
world, in the warmth and obscurity of their narrow home, rapidly 
mature, couple, and quickly begin to lay eggs, and that these 
