No. 569] 



ECTOPARASITES OF MAMMALS 



L>7H 



a well-distinguished other genus. There is no doubt that 

 the close physiological fitting of parasites to host makes 

 their host distribution significant of genetic or 1 'blood" 

 relationship, and this commonness of one type of parasite 

 to man and the apes, and its limitation to these hosts, and 

 replacement on the lower monkeys by another parasitic 

 type, is an added indication of the actual blood-likeness 

 of the Simians and man, a likeness apparently greater 

 than that between the Simians and the lower monkeys. 



Ill 



In the light of the plain statement in part I of this 

 paper of my belief gained from a study of the distribu- 

 tion of the bird-infesting Mallophaga, to the effect that 

 the host distribution of the permanent wingless ecto- 

 parasites of birds is determined more by the genetic rela- 

 tionships of these hosts than by geographic relationships 

 or any ecological condition, and the corollary of this, 

 which is that the distribution of the parasites may there- 

 fore often have a valuable significance as to the genetic 

 relationships of animals whose genealogic affinities are 

 in process of ascertainment, and in the light of the facts 

 of distribution for the mammal-infesting Mallophaga and 

 Anoplura as just set out in part II of this paper, I 

 hardly need to do more, in conclusion, than to point out 

 that the distribution conditions exhibited by the mammal 

 parasites, even in the face of the meager knowledge that 

 we yet have of the mammal-infesting forms, clearly, on 

 the whole, confirm this thesis. In fact, considering how 

 few mammal-infesting parasite species we yet know, it is 

 surprising how repeatedly the commonness of parasite 

 species to two or more related, although geographically 

 well separated, host species, is illustrated. All through 

 the order from Marsupials to Quadrumana this condition 

 is again and again exemplified. I am then, naturally, 

 made more certain of the essential truth of the thesis, and 

 can the more strongly recommend the attention of sys- 

 tematic zoologists to that practical application of it, 

 which I have stated in the form of a corollary. 



