114 ZOOLOGY 
budding of the embryos. In the Cestopa, the group in which 
parasitism has left the deepest mark, the whole alimentary system 
has disappeared leaving no trace, and the food is absorbed 
through the skin. In both groups the sense organs, for which 
they can have but little use, are very poorly or not at all 
developed. 
There can be little doubt that the Cestopa and TREMA- 
TODA are connected, or that the former have become more 
modified and departed farther from their common ancestor, 
than the latter. Lang’s researches lead him to look for the 
ancestors of the TREMATODA amongst the TURBELLARIA, and 
especially amongst the Triclades, which group contains some 
species not easily distinguished from the ectoparasitic Trema- 
todes, but for their ciliation. 
