TRYPANOSOMA 



389 



A. Development in the proboscis. 



B. Development in the anterior portions of the alimentary canal. 



C. Development in the whole alimentary canal. 



D. Development associated with infection of the salivary glands. 



E. Rectal encystment — faecal infection. 



F. Ovum infection. 



A. Proboscian Development.- — Roubaud has described a form of 

 asexual development of T. castellanii and T. hrucei in the proboscis 

 of Glossina palpalis in which the undulating membrane disappears; 

 the fiagellum is shortened, and the kinetonucleus approaches the 

 trophonucleus, while the parasite becomes attached to the wall 

 of the proboscis, and multiplies, forming masses of parasites, the 

 whole process occupying only a few minutes. 



Though he thinks that this method of development explains the 

 infection of man and animals by tsetse-flies in Africa, he was unable 

 to produce infection of susceptible animals by inoculation of these 

 forms. 



This form of development occurs 

 in T. vivax and in T. cazalhoui. 



B. Anterior Development. — Miss 

 Robertson has shown that the 

 trypanosomes of fresh -water fish, 

 when ingested by the leech Hemi- 

 clepsis marginata, first of all undergo 

 rapid multiplication by unequal 

 binary fission, giving rise to small 

 crithidial-like individuals, which 

 also multiply in the crop, and then 

 towards the end of digestion pass 

 forward as long, slender trypano- 

 somes into the proboscis sheath, 

 and are capable of infecting a new Fig. 91. — Proboscian Develop- 

 host; while the crithidial forms ^^^t. (After Roubaud.) 

 which remain in the crop become 



Leishmania-like bodies which multiply again when fresh blood is 

 ingested. The development of T. vittatce of the milk tortoise Entyda 

 vittata, takes place in a somewhat similar manner in the leech 

 Glossiphonia sp. (?) . 



C. Entire Canal Development.- — -This form of development is ex- 

 emplified by T . rajcB in the leech. Pontodella muricata, but in this case 

 the trypanosomes in the crop give rise to binucleate, rounded. 

 Leishmania-like forms without locomotor apparatus, which pass into 

 the intestine, where they become flagellate, and appear as crithidial 

 forms and multiply rapidly. During hunger periods they become 

 Leishmania-like bodies, only to revert to the crithidial form when 

 food is ingested. These crithidial-like forms become long, slender 

 trypanosomes, which pass forward into the proboscis and are the 

 infective agents. 



