NO. 



PARASITES METCALF IQ 



and ungulate hosts rather than descent from common ancestors. In 

 a second paper (1924a) Ewing discussed the host-parasite relations 

 of human and louse races and the hybridization of both and he includes 

 in this discussion prehistoric races of men and of their head lice, and 

 he mentions again the probability that the tropical American spider 

 monkeys {Ateies) acquired their head lice (Pediculus) "originally 

 from man but not from recent man." Two years later the same author 

 (Ewing, 1926) discusses further the significance of the geographical 

 and host distribution of the genus Pcdiculus. Four paragraphs of his 

 summary may well be quoted : 



1. In America two distinct groups of Pcdiculus exist, one of them confined 

 to man and one to monkeys. 



2. The forms infesting man are apparently largely hybrid races of head lice, 

 the pure strains of which were originally found on the white, black, red, and 

 yellow races of man living in their original geographic range. 



6. The monkey-infecting pediculids of America, so far as known fall into 

 distinct species according to the hosts they infest, thus indicating, to a certain 

 degree at least, a parallel host and parasite phylogeny. 



7. If these monkey hosts (Ateies, species) procured their lice from man it 

 was not from recent man but from human hosts that lived tens of thousands 

 of years ago— long enough to allow a species differentiation to develop among 

 the monkey hosts. 



Ward ( 1926) , in a presidential address before the American Society 

 of Parasitologists, has mentioned the importance of such uses of data 

 from parasites and refers in this connection to some of the work 

 reviewed in the present paper, 



Hegner (1928) discusses the protozoan parasites of monkeys and 

 man and concludes with the following statement : 



.... the protozoan parasites of monkeys and man belong for the most part 

 to the same species or are so similar in their structure, life-cycle and host- 

 parasite relations as to be practically indistinguishable. This situation is par- 

 ticularly striking when the protozoa of monkeys are compared with those ol 

 other animals associated with man. If the proposition that close relationships 

 of parasites indicate a common ancestry of their hosts is valid, then the facts 

 available regarding the protozoan parasites of monkeys and man furnish evidence 

 of importance in favor of the hypothesis that monkeys and man are of common 

 descent. 



This shows Hegner's recognition of the importance of host-parasite 

 data in studies of phylogeny. 



Some few students have attempted to minimize the importance of 

 parasite data in problems of biogeography (Noble, 1922, 1925 ; Dunn, 

 1925). Harrison (1924, 1926) has sufficiently answered their criti- 

 cisms. Noble's criticisms are based largely upon his new classification 

 of the Anura, a classification not as yet accepted by herpetologists. 



