224 University of Calif orntia Publicafions in Zoology [Vol. 16 



blepharoplast, requires but few changes to transform it into the chro- 

 matic basal rod of Trichomonas august a. This transformation may 

 happen by a shortening of the rhizoplast until that structure disap- 

 pears, leaving the parabasal body connected directly with the ble- 

 pharoplast, and stretched out along the margin of the body. Its con- 

 nection with the undulating membrane is a secondary modifieation 

 which further emphasizes its function as a kinetic reservoir. 



The only striking point of dissimilarity is found in the behavior of 

 this structure during division of the cell. In Trichomonas this does 

 not divide, but the old rod is retained by one daughter cell, while the 

 new one is formed by a new outgrowth from the blepharoplast in the 

 other daughter cell. Considering the original condition of the para- 

 basal body as an outgrowth from the blepharoplast, this in no way 

 hinders us from drawing the conclusion that in the chromatic basal 

 rod of Trichomonas we are dealing with a modified form of parabasal 

 body comparable, in probable origin and function, with the parabasal 

 body of the trypanosomes. That this structure differs widely in these 

 flagellates in form and apparent organization in no way invalidates 

 this conclusion, a view which is supported by the great variety of 

 form and structure exhibited by other organelles of the protozoan 

 body. For example, the nucleus may consist of but little more than 

 several masses of chromatin packed together without a membrane as 

 in some of the simpler Sareodina, or it may be built up of chromatin 

 and achromatin until a complicated structure is produced, such as is 

 found among the higher Sareodina which bears but little resemblance 

 to the simpler form. A third type, differing widely from either of 

 these, is found in Hexamitus intestinalis (Swezy, 1915), with its club- 

 shaped mass of chromatin, lacking apparent structure or membrane. 

 If the most important and essential organelle of the cell varies so 

 widely as these examples show, it would be expected that one devel- 

 oped under originally pathogenic conditions of parasitic life would 

 also exhibit great modification in its structure. The results of evolu- 

 tion among the Metazoa point to the same conclusion, namely, that 

 the effects of such evolutionary development are, more frequently 

 than otherwise, quite diverse in the ultimate forms they reach, but 

 remain comparable in origin and function. 



The greatest advance in complexity of the parabasal apparatus is 

 found in the parabasal bodies among the Trichonymphida, where 

 they are correlated with a corresponding complexity of cell structure. 

 This reaches its greatest development in Lophomonas blattarum. 



