30 University of California Publications in Zoology [Vol. 20 



lies in or near and parallel to the major axis of the body on the left 

 side of the eytostome within a short distance of the anterior end of the 

 body. It shows distinctly a peripheral clear zone which is somewhat 

 regularly chambered (fig. A, 1, 4, 5; pi. 3, fig. 9) as we have found it 

 also in Trichonympha. This zone surrounds the dark, dense and often 

 seemingly undifferentiated central chromatin mass. On heavy destain- 

 ing this central mass is at times resolved into fairly uniform rounded 

 granules (pi. 3, fig. 2) which appear to have some special relation 

 to the elements of the chambered zone, indicating the possibility of a 

 persistent organization of the nucleus. In some instances resting 

 nuclei (fig. B, 1; pi. 3, fig. 5) show large deeply staining granules 

 resembling nucleoli but these are as a rule absent. It is quite possible 

 that these may be end knobs of emerging chromosomes. 



The size of the nucleus ranges from 10 to 20jii in length whereas 

 that of the body ranges from 16 to 200^ or even more. Although 

 larger individuals have larger nuclei the increase in the volume of the 

 cytoplasm is many-fold greater than is the increase of the nucleus in 

 these giant forms. 



One of the most significant and striking features of the life his- 

 tory of T rich omit us in the digestive tract of Tcrmopsis is the repeated 

 and seemingly constant occurrence of large numbers of isolated neu- 

 romotor systems with the nucleus attached but no enveloping cyto- 

 plasm. It is evident that the delicate pellicle is easily destroyed, and 

 the labile cytoplasm escapes. Such an isolated structure In late pro- 

 phase with duplicated neuromotor systems but degenerate nucleus is 

 seen in plate 3, figure 11. These occurrences afford indisputable 

 evidence of the organic continuity and structural integration of the 

 neuromotor system of Trichomitus and of its direct and efficient 

 physical connection with the nucleus. One of us (Swezy, 1915a) has 

 noted a similar phenomenon in Hexamitus, a diplozooic polymastigote. 



Still more significant is the fact that such isolated systems are 

 still capable of flagellar aetivitj' and locomotion after the destructive 

 process of cytolysis of the cytoplasm. They continue to move for some 

 time in smears of the contents of the digestive tract mounted in tap 

 water. The very large number of isolated systems found in some 

 smears is indicative of a considerable period of persistence of the 

 isolated neuromotor system and nucleus after the loss of cytoplasm. 

 It is obvious that grave limitations on such activities must arise as a 

 result of the loss of the cytoplasm. The nucleo-cytoplasmic reactions 

 are suspended, nutrition is impeded if not wholly suspended, and 

 rapid exhaustion is accelerated by the loss. 



