1908.] 



A Trypanosome from Zanzibar. 



23 



Cultivation Medium used. 



The blood-agar medium used was made according to instructions kindly 

 sent by Prof. Novy. These need not be repeated here, as the details are fully 

 given by Novy and MacNeal in various papers. 



Cultural Characters of Trypanosoma lewisi. 

 A. Living, unstained. 

 Size. — Varies considerably in size. Some are not more than 1 or 2 

 microns long, not including the flagellum. Others are about the diameter of 

 a red blood corpuscle, while the usual length of the spindle-shaped cells is 

 15 to 20 microns. Some trypanosomes can be found at times which are 

 50 to 60 microns long. The greatest variation in size is found in young 

 cultures. 



Shape. — Trypanosoma lewisi varies greatly in shape, as well as in size. 

 Eound, pear-shaped, fusiform and slender forms are present in the cultures. 

 The round forms are usually found in old cultures, and are probably 

 involution forms. 



Contents of Cell. — The protoplasm in Trypanosoma lewisi, especially in young 

 cultures, is bright, glistening, and apparently homogeneous in structure in 

 the fusiform and slender forms. 



Undulating Membrane. — Not present as far as can be seen. The move- 

 ment of these cultural forms appears to be entirely due to the rapid motion 

 of the flagellum. 



Flagellum. — These forms possess, as a rule, a long free flagellum. In the 

 slender forms this is sometimes twice the length of the body. 



Motion. — The single, slender, cultural forms of Trypanosoma lewisi are 

 very active, and dart across the field of the microscope in a straight line. In 

 older cultures the round and other involution forms do not, as a rule, show 

 more than a slight swaying movement. 



Colonies or Aggregations. — Growth commences in a first generation about 

 the fifth day by the appearance of small rosettes composed of a few 

 trypanosomes. The colonies rapidly grow, so that on the following day 

 masses of wriggling trypanosomes may be seen. These aggregations of 

 twenty or more are attached by their flagella. They grow larger and larger 

 until, about the twenty-fourth day, they are apparent to the naked eye, and 

 consist of many thousands of trypanosomes. 



B. Fixed, stained. 



Protoplasm. — Homogeneous, as a rule. Vacuolation is rare, but sometimes 

 a large highly-refractile vacuole is seen. 



