218 University of California Publications in Zoology [VOL. 19 



suspended within the body, at times rupturing or displacing many 

 protoplasmic vacuoles. Small food granules, as Chlorella, are arranged 

 peripherally just underneath the periplast, showing that the suspension 

 capacity of the smaller peripheral vacuoles is greater than that of the 

 larger and more centrally located ones. The only evidence of circula- 

 tion of food vacuoles is that most of the undigested products are 

 evacuated from the posterior portion of the body. 



The sulcus has been described in discussing the various modifica- 

 tions of form but its chief features may be here summarized. It cleaves 

 one side, may extend anteriorly so as to cause a cordate or irregular 

 depression in the usual oval contour; posteriorly it may fade out, leav- 

 ing the general shape conical, or it may divide the body into two cups, 

 thus giving the bifurcated appearance ; by secondary branches, which 

 also tend to run longitudinally, there may be produced as many as 

 five posterior cusps. The whole of the sulcal region is amoeboid and 

 functions in food engulfing. Much of the irregularity of shape is due 

 to variations in this region. At its anterior end there is a depression 

 (pi. 9, fig. 19) which may function as a cytostome or esophagus. This 

 seems to end blindly, having no connection with any vacuole. If it 

 may at all be regarded as a cytostome, it is most primitive, more 

 potential and functional than structural. 



Collodictyon possesses a true vesicular nucleus, located anteriorly 

 near the base of the flagella and may be either centrally located or 

 displaced, usually away from the sulcus. It is surrounded by a distinct 

 nuclear membrane, from which granular cytoplasm extends out into 

 the body between the protoplasmic vacuoles. The large karyosome is 

 located centrally with a surrounding hyaline area. 



The blepharoplast is located anterior to the nucleus, at the base of 

 the flagella and immediately beside the depression caused by the 

 anterior extension of the sulcus. When killed and fixed in strong 

 Flemming and stained in Bordeaux red and iron haematoxylin, the 

 blepharoplast seems to consist of two basal granules surrounded by 

 a more darkly staining granular archoplasm (pi. 9, figs. 23-27). It 

 usually appears, especially when not sufficiently destained, as an 

 irregular chromatic mass in which are embedded the two basal granules 

 which protrude as tubercles, to each of which paired flagella are 

 attached, each also surrounded by a granular archoplasm (pi. 12, 

 figs. 19, 20). It is probable that the irregular chromatic mass is, 

 in fact, simply a lateral view of an archoplasmic plate or cap bound- 

 ing the granular area and in the center of which are the two basal 



