1919] McCulloch: Life Cycle of Crithidia and Trypanosoma 159 



preparations showing the process. In every instance of nuclear bud- 

 ding so far observed the chromatin has been peripheral, with a more 

 or less unequal distribution on the nuclear membrane. Frequently 

 there is one heavy mass with a uniform amount elsewhere on the 

 membrane (pi. 2, fig. 15). 



A somewhat larger, elongate flagellate, with sharply defined endo- 

 genous buds, is shown in figure 14, plate 2. Unlike the endogenous 

 forms just described the buds here are not posterior to the nucleus. 

 In figure 14, opposite the parabasal body, there is a bud decidedly 

 anterior and lateral in position. A second endogenous bud is also ante- 

 rior between the nucleus and parabasal body. Within all of these 

 nuclear structures the chromatin is massed irregularly upon the nuclear 

 membrane. 



In addition to these elongate flagellates undergoing multiple fission 

 of this type there are also pear-shaped crithidias (pi. 2, figs. 15-18) 

 containing several or numerous endogenous buds. Possibly it is the 

 greater thickness of these flagellates, with consequent decrease in 

 destaining capacity, which makes the buds within stand out so dis- 

 tinctly. Another marked characteristic of the pear-shaped flagellates 

 is the lack of differentiation between the nucleus and the buds. There 

 is no evidence of a parent nucleus which has given rise to the buds. 

 The distribution of the chromatin within these buds presents some 

 interesting variations. In figure 15 the buds contain a clearly defined 

 chromatin encrusted nuclear membrane together with one distinct mass 

 or chromatin granule. In figure 17 the massing of the chromatin may 

 mean a more advanced stage since it is no longer on the entire nuclear 

 membrane but has been segregated into two masses, which give the 

 buds a bipartite appearance. Proceeding to figure 18 in this pear- 

 shaped individual more steps in advance are portrayed, namely the 

 unused portions of the flagellate are beginning to degenerate around 

 the endogenous buds. The parabasal body has already disappeared, 

 and only a portion of the discarded flagellum remains near by. The 

 structure of the endogenous buds of this spherical crithidia is remark- 

 ably uniform. In each bud the chromatin granule is adherent to 

 the nuclear membrane. 



Other elongate flagellates undergoing multiple fission are observed 

 in figures 19, 20, and 21. Some interesting variations can be pointed 

 out in these crithidias. In figure 19 there is a nuclear rhizoplast, 

 which can be traced from the edge of the nuclear membrane to the 

 blepharoplast. Of greater interest are the variations shown in figures 



