342 DR. A. E. SHIPLEY ON | Mar. 16, 
result in the discovery of many other objects. The important. 
fact from our point of view is that the expelled feces contain 
ova within which are fully formed larve ripe for hatching. 
But we have also found hatched larvee in the feces which were 
still in the rectum, so we may conclude that the droppings may 
contain (1) larve coiled in the egg-shell, and (2) larve which 
have escaped from the egg-shell and are living freely. 
No one has ever seen, and probably no one will ever actually 
see, one of these eggs or larve of the thread-worm enter the body 
of the grouse, but that they do so directly is, I think, unquestion- 
able. Railliet* and Ransom tT have both succeeded in infecting 
rabbits by directly feeding them on the embryos of 7. retorte- 
formis ; and presumably the development of 7. pergracilis is also, 
like that of its congener, accomplished without an intermediate: 
host. In Ransom’s case the embryos apparently hatched out and 
developed to the ensheathed stage within two weeks after the 
passage of the eggs from the intestine of the host, and the 
embryos when swallowed by a second rabbit became mature and 
capable of laying eggs in about a month after they had been 
‘swallowed. The thread-worms exist in hundreds in every bird ; 
the female thread-worms, which greatly exceed the male thread- 
worms in number, lay thousands of eggs. The eggs and larvee 
exist in countless numbers in all grouse-droppings. As these are 
disintegrated by rain and frost, these minute organisms are either 
washed by the water on to all the food or pebbles a grouse may 
pick up, or in the absence of rain are dried and blown by the 
wind all amongst the heather and other food which a grouse may 
eat. The ova and larve of thread-worms are notoriously resistant 
to the effects of desiccation, so that even in the event of prolonged 
droughts—which, judging from my experience of Scotland, must 
be a remote contingency—the eggs and larve are in no way 
prevented from reaching their host <. 
During a visit to Beaufort Castle in August, 1908, I introduced 
what has since, in the hands of Dr. E. A. Wilson, proved a 
valuable instrument in research. We had hitherto been unable 
to find the ova or the young nematodes upon the heather; they 
are so minute and require so high a power of the microscope to 
see them, that all attempts to look at them on the stalks or in 
the buds had failed. The new method showed that nematodes, 
some of them free-living, and their larve and the larve of 
parasitic forms exist in countless thousands im every square foot 
of heather. 
The method consists in soaking a handful of heather in a glass 
bottle, using just as little water as will well cover the twigs, for 
several hours—overnight is not too long; then shaking the bottle 
well for some minutes, or shaking it more gently in a rocker 
* Bull. Soc. Zool. France, xiv. p. 375. 
+ U.S. Dept. Agric., Bureau Anim. Industry, Circular 116, 1907. 
~ Since the above was written, Mr. R. T. Leiper has obtained all the stages of the 
life-history of 7. pergracilis and has succeeded in infecting hand-reared grouse 
which were previously free from the worms. 
