NO. 8 PARASITES METCALF 21 



flagellates living in their intestines. Approximately fifteen hundred 

 species of termites are known and from all tropical and many tem- 

 perate parts of the world. They have a highly elaborate taxonomy 

 with four families, subfamilies, genera, subgenera, species and sub- 

 species, and the genetic relationships and the phylogeny seem capable 

 of successful study. Forty-six genera comprised in 12 families of 

 termite flagellates have been described from less than 40 species of 

 termites, this being but a meager beginning of the taxonomic and 

 phylogenetic study needed for this truly vast number of mostly unde- 

 scribed species. It seems unlikely that any other organisms will lend 

 themselves so favorably to host-parasite studies as will the termites 

 and their flagellates. Every individual termite is richly infected. The 

 wealth of species of these hosts and of their Protozoa is so great as 

 to be somewhat awesome. "There are probably more flagellate 

 Protozoa in the intestines of termites than in all other animals com- 

 bined." ' It is a bold student who attacks these groups with the idea 

 of employing them b\- the von Ihering method, but the one who does 

 so should reap a rich reward. 



The termites are a peculiarly favorable group for such studies be- 

 cause, in addition to their varied internal fauna of flagellate parasites, 

 they harbor, either customarily or occasionally, representatives of 

 every other group of parasitic Protozoa (Amoebae, Ciliates, Sporozoa) 

 so that one studying them through their flagellates would often be 

 able to check up results from some of their other parasites. 



The Chlamydozoa are but little understood. It seems not unlikely 

 that when better known, especially if they prove to be associated with 

 mozaic and other filtrable virus diseases, they may prove of much 



interest. 



The Sporozoa offer much fine material for host-parasite studies, 

 all being parasitic. Most species of terrestrial and fresh water animals 

 harbor representatives of one or more of the numerous groups of 

 Sporozoa, and they infect also very many marine animals. Many 

 Sporozoa, perhaps most of them, show a high degree of specificity m 

 their selection of hosts, being confined each to one species of host or 

 to one taxonomic group of hosts. This renders their evidence m 

 some instances peculiarly convincing. _ _ 



Among ciliate Infusoria are numerous parasitic species. Balantidmm 

 and Nyctothcrns, parasites of man and other mammals, should be 

 valuable for host-parasite studies. The "Astomata," which include 

 several perhaps unrelated families, should also furnish favorable ma- 



' Cleveland, L. R.. quoted from a letter. 



