"GROUSE DISEASE " COCCIDIOSIS 261 



caused the birds to die from want of water. We now know that 

 young Grouse chicks seldom, if ever, die of thirst, 1 whereas 

 we also know that dry heat is not unfavourable to the 

 development of the oocysts. 



Having ascertained by experiment that moisture and cold Effects oi 

 had a retarding effect upon the development of the coccidian variation 

 cysts, and that dry heat appeared to assist it, it became neces- the moor 

 sary to learn whether the variations of climatic conditions on the 

 moors produced similar results as shown by the mortality 

 observed among the young stock. 



In this stage of the investigation it was found that the 

 reports of the Committee's local correspondents for the years 

 1906, 1907, and 1908 were of the greatest value. 2 



These reports are rather difficult to interpret, owing to the 

 fact that in some cases the stocks suffered heavily from Stron- 

 gylosis among the adult birds, and drowning among the chicks, 

 thus causing a reduction in numbers which could in no way be 

 connected with Coccidiosis. One or two points, however, are 

 significant. In the first place, in the years 1906 and 1907, 

 though the nesting and hatching seasons were everywhere very 

 wet and cold, and there was a heavy loss of chicks from drowning, 

 there is nothing to indicate that the young stock was affected 

 by disease of any kind, and as a whole they appear to have 

 survived in greater numbers than was then expected. In 

 1908, on the other hand, when the spring and summer were 

 exceptionally warm and dry, and no young birds were reported 

 as drowned, many observers noted a disappearance of the young 

 Grouse for which they could not account. 



After 1908 the annual reports were discontinued, but the 

 year 1911 was marked by such an exceptional* drought that 

 an additional report was obtained for that year with a view to 

 the further elucidation of the subject. The answers received 

 from one hundred and forty correspondents, while un- 

 expected in some respects, went far to establish the hypotheses 

 based on experiment. There was no universal outbreak of 



1 Vide chap. iii. p. 105. 2 See pp. 273 et seq. 



