TRYPANOSOMES OF AQUATIC REPTILEsS 587 



microns in breadth. The shortest forms were about 25 microns long and 

 4 to 5 microns broad. Intermediate forms also occurred. The undulating 

 membrane is markedly frilled. The fiagellum measures up to 25 microns 

 in the large and small trypanosomes, being relatively longer in the latter. 

 In the large forms the body is seen to be longitudinally marked by parallel 

 lines, an indication. of myonemes. When examined in the fresh condition, 

 the trypanosome is seen to writhe about locally with little progression. 

 Occasionally there is a slow translatory movement, the trypanosome 

 revolving spirally on its axis. In the blood of the tortoise division stages 

 were rarely found, and these only in the case of trypanosomes of the 

 intermediate size. It is possible that active multiplication only takes 

 place in the early stages of an infection, or is chiefly confined to the internal 

 organs. 



In the crop of the leech a cycle of development takes place, resulting in 

 the formation of crithidia forms (Fig. 237, 5-10). The earliest stage of 

 this cycle consists in the rounding-of! of the large trypanosomes, a process 

 which can be studied in fresh blood-preparations under the microscope. 

 The large trypanosomes become retracted in various ways to form globular 

 masses of cytoplasm. The myonemes cease to be visible, as also the nuclei. 

 The axonemes become detached from the membranes, and finally disin- 

 tegrate. These globular bodies then commence to divide. By two 

 divisions four pyriform bodies are produced from each, and these remain 

 more or less attached to one another while they form flagella. The latter 

 first appear as short rods, which increase in length till their full size is 

 reached. These flagellate bodies, when stained, are found to have the 

 crithidia structure. By their further multiplication the crop of the leech 

 becomes populated with a large number of long, slender, and very actively 

 motile crithidia forms, which eventually give rise to metacyclic trypano- 

 somes (Fig. 237, 11-13). The development appears to be limited to the 

 crop, and the exact mechanism of the infecting process was not elucidated. 

 The leech, Glossosiphonia sp., is peculiarly suited to play the part of an 

 intermediate host, as it has the habit of wandering from one tortoise to 

 another. 



Other Trypanosomes of Aquatic Reptiles. 



Trt/panosoma danwnice, the first trypanosome to be described in a reptile, 

 has been mentioned above. It was discovered by Laveran and Mesnil (1902). 

 The length was 32 microns, of which the fiagellum formed about one-third, 

 and the breadth 4 microns. Trypanosomes have been met with in a 

 number of other chelonians. Button and Todd (1903) and Button, Todd, 

 and Tobey (1907) noted the presence of trypanosomes in tortoises of the 

 Gambia, as did Minchin (1910) in one in Uganda. Bouet (1909) gave the 



