1915] McCuUoch: CritJiidia leptocoridis 9 



to 2jii in diameter (pi. 1, fig. 1), there is obviou.sly a period of rapid 

 growth. The spores are well protected by a thick, light browni mem- 

 brane and it is only with difficulty that the nuclear structure can be 

 observed in the stained material. There is some evidence, very slight 

 to be sure, that two developmental form.s occur in CritJiidia lepto- 

 coridis, one a non-flagellated form (pi. 1, fig's. 4r-7) enclosed in a 

 capsule-like structure, and a flagellated form which develops from 

 the small, round spores (pi. 1, figs. 1-2). 



The non-flagellated forms (pi. 1, figs. 3, 7, 10, lib, lob) are readily 

 destained. The nucleus is usually found in the posterior part of the 

 body. The chromatin stains deeply and may be in the form of one 

 or more granules (pi. 1, figs. 7, 10, 166, 216). From the central 

 chromatin mass there is a network extending out to the nuclear mem- 

 brane (pi. 1, fig. 6) in the form of radiating fibers. This is a very 

 characteristic structure and often serves as a means of identification 

 of Crithidia leptocoridis. 



These non-flagellated forms do not show all the extranuclear or- 

 ganelles found in the mature flagellates. The "kinetonueleus" is not 

 clearly shown in the early stages. Later two chromatin granules lying 

 in close proximity are present. The rhizoplast is readily distinguished 

 in some forms (pi. 1, figs. 176 and 196) in which it passes forward 

 from the nucleus to the kinetonueleus and thence out to the anterior 

 end of the body. The presence of an "axostyle" has not been ob- 

 served as yet in these forms. 



The flagellated forms come from the oval spore forms (pi. 1, figs. 

 1, 2, 8, 9, and 11). These are at once characterized as small forms 

 vigorously rotating about by means of a well-developed flagellum and 

 imdulating membrane (pi. 1, fig. 11). Like the non-flagellated forms 

 of the preflagellate stage, they occur in the stomach of the yoimg 

 nymphs and the infection is usually light. The cytoplasm shifts and 

 in a short time there is formed a pear-shaped organism. These forms 

 are not unlike some of the " Initialf ormen " figured (pi. 11, fig. 48) by 

 Chagas (1909) in the life-cycle of Schizotrypanum cruzi. The com- 

 parison might be carried still further, pointing out the presence of 

 two types among his " Initialf ormen " (pi. 11, figs. 49-60) found in 

 the mid-intestine, a flagellated, and a non-flagellated form. 



The nuclear structure of the flagellated forms is essentially the 

 same as that of the non-flagellated forms. The nucleus is relatively 

 large and is located in the extreme posterior end of the body at first. 

 Later it becomes more central. Here again the chromatin material is 



