" GROUSE DISEASE " COCCIDIOSIS 249 



segments or daughter-germs are known as merozoites. The 

 number of merozoites formed from a single schizont seems to 

 vary ; eight to fourteen are common numbers, but as many as 

 twenty have been found. 



The groups of merozoites now break up, and each free germ 

 seeks out and enters an hitherto uninfected cell in the lining of 

 the gut, and there each daughter-germ undergoes multiplication 

 as before. Several generations of schizonts and merozoites are 

 thus produced, each generation representing an enormous increase 

 in the infection. When it is realised, that after passing through 

 the multiplicative process four or five times, the original germ 

 may be represented by many thousands of similar germs, it 

 will be understood that they must exercise a very destructive 

 effect upon the gut lining of the host, and this engenders the 

 fatal illness in the young chick. 



Sooner or later a limit is reached, both to the power of the 

 Grouse chick to provide nourishment for the parasite and 

 to the multiplicative capacity of the parasite itself, and when 

 the circumstances become thus unfavourable to further multi- 

 plication, the parasite enters upon a new phase with a view to 

 the perpetuation of its species, and produces forms capable of 

 infecting fresh birds. 



The schizonts now cease to develop into groups of merozoites, Sexual 

 but instead slowly give rise to male and female organisms. 

 The female organism, containing much food-material, is known 

 as a macro-gametocyte (Fig. 36, I, ? ), and eventually gives rise 

 to a single macrogamete (Fig. 36, J, ?). The male parent cell, 

 or micro-gametocyte (Fig. 36, 1, <? ), multiplies, on the other hand 

 (Fig. 36, J, ), and produces a number of small, active, male 

 germs known as microgametes (Fig. 36, K, ^). 



When the macrogamete or female parasite has attained 

 its maximum development, it invests itself with a cyst wall, 

 and often lies in the lining of the gut near the outer edge of the 

 tissue. The minute but active microgametes or male germs 

 meanwhile have broken away from their parent cells, and have 

 swum out into the gut with rapid lashing movements of their 



