226 University of Calif oniin. Publications in Zoologn IVol. 16 



from one period to anotlier, shown by their constantly changing shape, 

 size and position. The chemical constitution of these bodies apparently 

 varies greatly at different periods and in different cells. Further 

 work on the subject from both the metazoan and protozoan standpoint 

 is needed before any adequate generalization can be made, and yet 

 certain resemblances can be traced which seem to be of some sig- 

 nificance. 



The parabasal bodies shown in figures 20 to 33, exhibit a great 

 variety of sizes, shapes, and positions, as do also those grouped in 

 figures 34 to 41. The same thing is found in any group of trypano- 

 somes, as may be seen in the plates of Chagas (1909), Minchin and 

 Thompson (1915) and others, though the variation is less in these 

 forms than in the flagellates Trypanoplasma and Prowazekia. This 

 might be expected from a comparison of the media in which these 

 flagellates live, the blood forming a more nearly constant medium than 

 does the intestinal contents with its constant fluctuations in both 

 quantity and quality. 



Considering the parabasal bodies as related in their origin and de- 

 velopment to the processes of metabolism it seems not improbable that 

 these structures may be homologous to the mitoehrondria in the meta- 

 zoan cell. 



The parabasal bodies of the Triehonymphida are structures re- 

 lated to the blepharoplast, the kinetic center of the cell, and, in two 

 cases at least, are formed by direct outgrowth from it. They are per- 

 manent cell organelles, persisting from one division cycle to the next. 

 Janicki (1911) has described their composition as "an fixierten und 

 gefarbten Preparaten, besonders an osmierten, als aus dichten, durch- 

 aus homogenen Plasma zusammengesetz ; seine Konturen sind nicht 

 sehr scharf ausgedriickt ; eine Membran, welche das Plasma um- 

 sehlosse wird nicht beobachtet." With these, as is also the case with 

 the chromidial bodies of Prowazekia, all stains, as, for example, Dela- 

 field's haematoxylin, do not produce nuclear reactions. This proves 

 that it is not composed of nuclear chromatin, or at least not of un- 

 modified nuclear chromatin. It will be pointed out in greater detail 

 below that the parabasal body of trypanosomes is also not composed of 

 nuclear chromatin in the sense that it is chemically identical with the 

 intranuclear material. 



In his latest communication, which appeared as this article was 

 being prepared for the press, Janicki (1915) has extended the appli- 

 cation of the term "parabasal body," including under that heading 



