THE PROTOZOA OF TERMITES 



39 



survive for any length of time outside of the termites and species 

 of termites are isolated from one another, the possibilities of cross- 

 infection are slight. It is to be expected that the presence of certain 

 flagellates in termites will throw light on the relationship of species 

 and the origin of genera, families and subfamilies in the isoptera. 

 Also their presence, as that of certain opalinid^ in frogs and 

 toads, will serve to indicate the relationship of hosts in different 

 geographical regions, and the directions in which those hosts have 

 carried their entozoic protozoa. In a survey of the uses to which 



Fig. 10. — A, Holomastigotes elongatiim Grassi from Reticulitermes hes- 

 perus. B, Holomastigotoides hemigymniim Grassi from Leucotermes tenuis. 

 C, Spirotrichonympha flagcllata Grassi from Reticnlitermes Incifiigus. A, 

 original ; B, after MacKinnon ; C, after Grassi. 



host-parasite data have been and may be put to assist in the solu- 

 tion of problems of genetic relationship among organisms, geo- 

 graphical distribution and paleogeography, Aletcalf (1929) states 

 that "it seems unlikely that any other organisms will lend them- 

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

 and their flagellates." Our present knowledge shows the value of 

 the intestinal faunas for studies in the classification and phylogeny 

 of the ISOPTERA, but is far too incomplete for the problem of 

 geographical distribution. There is, however, a small amount of 

 data which has significance for the latter question. 



The following general observations on the problem of the dis- 



