24 University of California Publications in Zoology [Vol. 20 



The factors conducing to these changes in form ai'e the stages of 

 general contraction of the body, the mass of food vacuoles which is 

 usually greater in the more rounded forms, and the proportional 

 length of the parabasal body and undulating membrane. As a result 

 of multiple fission (pi. 4, figs. 28, 30) one of the daughters receives 

 the ancestral parabasal and two of its associated flagella, both of which 

 are disproportionally large for the cytoplasmic mass of this schizont. 

 Kegulative resorbtion, in (pi. 4, fig. 31) or out of a cyst, or rapid 

 cytoplasmic growth, would be necessary to readjust the volumetric 

 relation of the neuromotor system and the cytoplasmic mass. 



The range in size in this species is very considerable (fig. A, 1-7). 

 The smallest sehizonts we have recorded (pi. 4, fig. 32) are but 16/i 

 in length while the largest exceed 200/i. These giant individuals are 

 probably approaching multiple fission. They rarely survive the 

 smearing operation intact. Not infrequently the nucleus and its 

 attached neuromotor system of such giant individuals will be found 

 intact and still active after the loss of the cytoplasm indicating that 

 this stage is particularly susceptible to destruction under normal con- 

 ditions in the host. IMost of the individuals seen range from 75 to 

 125yu, in length. 



The organs of T rich omit us (fig. A, 5) consist of the cytostome 

 (cyt.), nucleus (/(.), food vacuoles (/. vac), and the neuromotor organ 

 system. We will now consider these organs with the cytoplasm in 

 detail. 



Cytoplasm 



The cytoplasm of Trichomitus termitidis is reasonably labile, finely 

 granular, and somewhat alveolar in structure. This labilitj^ may be 

 the cause of such abnormal proportions (such as are seen in plate 4, 

 figure 30) rather than the inheritance of the ancestral parabasal sug- 

 gested above. The dropping off by plasmotomy of the labile cyto- 

 plasm has been observed by us in Trichomonas augusta (Kofoid and 

 Swezy, 1915). No contractile vacuole is present but food vacuoles 

 (fig. A, 5, /. vac.) are found everywhere within the body except about 

 the nucleus. These contain fragments of cellulose from the digestive 

 tract of the termite or eoccoid bodies, possibly bacterial (pi. 3, fig. 5). 

 Defecation of undigested fragments has not been seen. 



Upon treatment with neutral red a large number of food particles 

 or metaplasmic droplets stain deeply. They lie scattered throughout 

 the cytoplasm and are larger near the center of the body (fig. A, 8). 



