Preliminary remarks on immunity in animal kingdom 51 



rounded and fused together, but the nucleus and the haemo- 

 globin enable us to recognise them without any difficulty. Later 







FIG. 7. Intestinal ceU of a 

 Planarian, filled with red 

 blood corpuscles, undergoing 

 digestion, of the goose. 



FIG. 8. Digestion of red blood 

 corpuscles of the goose with- 

 in an intestinal cell of a 

 Planarian. 



he red colouring matter begins to diffuse into the digestive vacuoles 

 which form around the corpuscles. These corpuscles empty them- 

 elves, retaining their nuclei and capsules, which shrivel more and 

 more. The nucleus also undergoes almost complete digestion, its 

 membranous layer alone persisting (fig. 8). Even several days after 

 ;he digestion of the blood has begun one can still find debris of 

 >erfectly recognisable red corpuscles, but the red colour has been 

 eplaced by a more or less pronounced brown tint. In the last 

 stage of the digestive process, as the red corpuscles disappear, the 



42 



