degree of consangmnity of the hosts will play a lesser role than the 

 similarity of food and conditions of existence. At the sanne tinne, however, 

 one must not forget, as has already been indicated, that the consanguinous 

 relations of hosts find reflection both in a similar form of life and in 

 alimentation whichfacilitates a more rapid transfer of parasites on related 

 hosts. 



Summing up, one can consider that the peculiarities of mono- 

 genetic trenaatodes noted by us, starting from their species and ending 

 with their families reflect the schemes of historical interrelations about 

 which we spoke earlier. Consequently, it seems to us that we can make a 

 very definite conclusion in that with the establishnnent of consanguinous 

 relations of the parasites --particularly of monogenetic trematodes, it is 

 fully possible to utilize the analysis of their occurrence on the hosts as a 

 method of phylogenetic research. This conclusion, as we know, is not new, 

 but the discussion which has been carried out, it seenns to us, puts it on a 

 more solid base and allows us to evaluate more critically the results which 

 are obtained when we apply the present method. 



^^C^CjVCA/. 



346 



