314 The American Naturalist. April, 
of regions of the globe which are exempt, or very nearly so, 
from this disease [Faroé Islands] there are others where carci- 
nomata are very common.” According to Cohnheim’s theory 
of a simple overgrowth of embryonic survival tissues, the 
average of victims to cancer should be the same in every part 
of the world, and liability to its ravages should be common to 
all the Metazoa. Metschnikoff points out another feature 
which cancers have in common with coccidian diseases—the 
exaggerated proliferation of the epithelial cells in the affected 
organs. How close the resemblance is, the following figures 
show. 
FIGs O: 
Hyperplasia of the biliary ducts of the rabbit under the influence of coccidia. 
As yet, the study of parasitism in cancerous diseases is w 
beginning. The coccidia of the rabbit have been know? 
