10 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 8l 



communicable disease occurring at the time of the discovery of America on 

 either the eastern or the western continent exclusively probably originated on 

 that continent. Any communicable disease belonging at that date equally to 

 both halves of the world may probably be referred to a time at least as remote 

 as that when the American race separated from the rest of mankind. 



At least two other students came independently to the same realiza- 

 tion of the importance of host-parasite data, Launcelot Harrison 

 being the next. In 1911 he discussed genetic relationships of hosts 

 on the basis of their parasites, and strangely enough it was the birds 

 and their Mallophaga which first brought to him, as to Kellogg, this 

 conception of the use of parasite data. I have not had access to the 

 original record of this first discussion by Harrison, but he later refers 

 to it as follows : 



My personal connection with this subject dates from 191 1, when, after about 

 a year's study of Alallophaga, I read a paper before the Sydney University 

 Science Society upon the possible value of these parasites in determining bird 

 affinities. The manuscript of this paper has been lost, but an abstract was 

 published in the annual report of the Society for 1911-12, which I quote to show 

 that I had already arrived at some definite conclusions in advance of/ and 

 independently of, Kellogg : 



Wednesday, i6th August (1911). — Held in the Geology Theatre, the Presi- 

 dent in the chair. L. Harrison read a paper, illustrated with lantern-slides, on 

 "The Taxonomic Value of Certain Parasites". The parasites referred to are 

 the biting lice (Mallophaga) found upon birds or mammals. Owing to both 

 environment and food remaining unchanged through the centuries, these insects 

 have not differentiated as fast as their hosts, and aft'ord indications of original 

 relationship between birds that have diverged widely from parent stock. Though 

 birds can be divided into good natural groups, the relationships between these 

 groups have not, and cannot, be satisfactorily determined on anatomy alone. 

 So any line of investigation that is likely to aid the solution of bird phylogeny 

 deserves consideration. Some evidence is afforded confirming parts of existing 

 classifications. Among other results, a study of the Mallophaga would suggest 

 the inclusion of the penguins with the fowls, pigeons, and tinamous, a relation- 

 ship that has never before been suggested. Such results could, of course, only 

 be put forward as suggestions to the morphologist. A preliminary examination, 

 however, of this group of parasites, certainly suggests that more complete 

 knowledge will afford valuable clues towards the solution of bird taxonomy. 



Between 1914 and 1922 Harrison published seven more papers 

 discussing Mallophaga of birds and bird relationships. In 1924, he 

 discussed at some length the former connections of Antarctica with 

 other southern lands, quoted my own work on evidence from the 

 Anura and their opalinid parasites and came to its support with bio- 

 geographic evidence and also with further host-parasite data from 



^ Kellogg antedated Harrison in this use of parasite data to determine bird 

 relationships, but the realization of the importance of such data came to Plarrison 

 independently. Later he saw that much wider groups of problems are approach- 

 able through the host-parasite method, and his papers since 1924 discuss some 

 paleogeographical questions connected with Australia, using host-parasite data. 



