1909. } ON THREAD-WORMS OF THE RED GROUSE. 399 
2. The Thread-Worms (Nematoda) of the Red Grouse 
(Lagopus scoticus). By A. E. Surpiey, M.A., Hon. 
D.Sc., F.R.S., F.Z.S., Fellow and Tutor of Christ's 
College, Cambridge, and Reader in Zoology in the 
University. 
[Received December 12, 1908.) 
(Plates XLVIIL-LV.*) 
NEMATODA. Thread-worms or Round-worms. 
(i.) Family Strongylide. 
(i.) TRICHOSTRONGYLUS PERGRACILIS (Cobbold). 
Synonym: Strongylus gracilis Cobbold. 
History. 
This round-worm was first described under the name of Stron- 
gylus pergracilis Cobbold, by Cobbold + whose words we quote :— 
“ Characters.— Body filiform, finely striated, gradually dimi- 
nishing in front, uniform in thickness below; head bluntly 
pointed, with a simple oral aperture; tail of the male furnished 
with a bilobed bursa, each half supporting four pointed rays; 
spicules two, thick, and slightly divergent; tail of the female 
slightly swollen above the subterminal anal orifice, rather sharply 
pointed at the tip; vaginal opening situated at the upper part of 
the inferior sixth of the body. 
“Length of male 3" to 2”; body =4," in diameter, tapering 
anteriorly to Z000, at the head; greatest breadth immediately 
above the bursa ashy: 
“ Length of female mostly 2 2 sometimes very nearly 3” 
breadth above = tail 4,” to ;4,’, narrowing at the extreme 
point to —),,’ ieee diameter of the eggs 1,", their 
breadth being =1,"'.” 
Eight years later Cobbold described, under the name of 
S. douglassii, a nematode which occurred in great numbers in the 
proventriculus of certain South African ostriches. Their presence 
was associated by the ostrich-farmers with a certain amount of 
disease and with some deaths. 
Two other allied forms, Trichostrongylus (Strongylus) nodularis 
and Trichostrongylus (Strong ylus) tenuis, are also held to cause 
disease in birds, whilst recently a fifth form, S. quadriradiatus 
(possibly also a Trichostrongylus), has been added by Stevenson $ 
to the list of the Strongylids harmful to birds. 
id 
* For explanation of the Plates see P. 349. 
Mee ‘The Grouse Disease,’ ‘ The Field ’ Office, London, 1873. 
{ J. Linn. Soc. London, Zool. xvi. 1883, p. 184. 
§ U.S. Dept. Agric., Bureau Anim. Industry, Cirenlar 47, 1904. 
