Lirypens entoparasiter. sis 37 
loped into the well known cronic condition. Still we have observec 
some specimens stronger infested (See the list page 11). The 
nuinbers of Eimeria here quoted are counted in one preparation 
from each of the different parts of the intestine. Two of these birds 
(one of them a small chicken) showed the infection in a fresh state 
of development, with many intracellular stages of the parasite. 
The distribution of the parasites in the different parts of the 
intestine was not the same as was found in the Red Grouse. In 
the Willow Grouse especially the jejunum was infested; in 28 
birds we found Eimeria in this part of the intestine, while it was. 
lacking in the duodenum. Perhaps this is the typical picture of 
the cronic infestion. 
Numerous examples taken from observations in the field during 
the summer shows to evidence, that the decrease of the Willow 
Grouse is due to a very great mortallity between the young chickens,. 
and when we know, that a very great number of adult Willow 
Grouse are infested with Eimeria, and can act as spreaders of the 
disease, there can be very little doubt but, that Coccidiosis is the 
cause — or in any case the principal cause — of the great decrease 
in numbers characteristic for the Willow Grouse the last few years. 
Eimeria avium also attacks the Black cock (Tetrao tetrix, L.) 
and the Capercaillie (Tetrao urogallus, L.), and as a considerable 
number of dead specimens of these birds were iound last authum, 
there is hardly any doubt about, that these latter too are suffering 
from Coccidiosis, and last year they showed the same fatal 
decrease in numbers as experienced with the Willow Grouse. 
As the greatest part of the material was sent to me preserved 
in formaline, the majority of other unicellular parasites could not 
be determined. The Spirochæta lovati, by Fantham described 
from the Red Grouse, makes an exception; it was found in the 
czcum of 30 birds and often present in enormous numbers. As 
far as can be judged from the weigth of specimens infested with 
this parasite, the Spirocheta is doing no harm to the birds. 
Of tape-worms we found the Hymenolepis microps in the 
duodenum of 10 birds, in four cases the parasite was present in 
great numbers as has been described from the Red Grouse. 
Davainea urogalli is a very common parasite in the Willow 
Grouse and is widely distributed over the whole country; the 
Worm was found in 32 birds and frequently in so large numbers, 
