TRYPANOSOMA GAMBIENSE 



75 



infected blood, sooner or later multiplication occurs. This develop- 

 ment usually begins in the middle or posterior part of the mid gut, 

 and (rypanosomes of varying sizes are produced. After the tenth 

 or twelfth day, many long, slender trypanosomes (fig. 30, a) are 

 found, which gradually move forwards into the proventriculus. Such 

 long, slender forms represent the limit of development in the lumen 

 of the main gut. The proventricular type, developed about the 

 eighth to the eighteenth or twentieth day, is not infective ; it may 

 occur in the crop, but is not to be found permanently there. 

 Between the tenth and the fifteenth days multi nucleate forms of 

 trypanosomes are found, and may be styled multiple forms (fig. 30, 6). 

 Some of these latter may be degenerative. 



FIG. 30. Trypanosoma gambiense. Development in the fly, Glosnna palpalis. a, slender, 

 proventricular form; b, multinucleale form; c, d, crithidial forms; e, infective type of 

 trypanosome found in salivary gland. x 2,500. (After Robertson.) 



Invasion of the Salivary Glands of the Fly. Long, slender trypano- 

 somes from the proventriculus pass forward into the hypopharynx. 

 They then pass back along the salivary ducts, about sixteen to thirty 

 days after the fly's feed. The trypanosomes reach the salivary glands 

 as long, slender forms. In the glands they become shorter and 

 broader, attach themselves to the surrounding structures, and assume 

 the crithidial facies (fig. 30, c, d). As crithidial forms they remain 

 attached to the wall and multiply in the glands. These crithidial 

 stages differentiate into the short, broad trypanosome forms, capable 

 of swimming freely (fig. 30, e). 



Miss Robertson considers the development in the main gut to be 

 indifferent multiplication, and that salivary fluid seems necessary to 

 stimulate trypanosomes to the apparently essential reversion to the 



