TRYPANOSOMES OF FISH 605 



flagellates of various types occurs during the middle period, when the blood 

 is being digested into a green-brown fluid (Fig. 247, 12-14). In the third 

 period of digestion the crop or stomach becomes nearly empty, and long, 

 slender, very active flagellates of the typical trypanosome type appear. 

 These forms migrate forwards, and presumably find their way into the 

 proboscis sheath, though this is not actually mentioned (Fig. 247, 15-16). 

 The whole developmental process is very similar to that of T. vittatce of the 

 tortoise described above. It is presumably the long narrow trypanosomes 

 of the proboscis which bring about infection of the vertebrate. 



The development of T. gmnulosum of the eel in Hemiclepsis, as de- 

 scribed by Brumpt, is very similar to that of T. rajce. At the end of 

 twenty-four hours after feeding, however, flagellates had vanished from 

 the stomach, and were undergoing development as leptomonas (? crithidia) 

 forms in the intestine, whence they eventually migrated to the stomach 

 and along the oesophagus to the proboscis and its sheath, where the meta- 

 cyclic trypanosomes were to be found. 



According to the observations of Brumpt (1904-1906), the trypanosomes 

 of fresh-water fish are carried by Hemiclepsis marginata, in which the 

 development is of two types (Fig. 240). 



I. The trypanosomes develop in the stomach alone, and here the 

 crithidia forms and eventually the metacyclic trypanosomes appear. 

 There is no infection of the intestine nor of the proboscis sheath. Infection 

 of the fish takes place by active migration or regurgitation forwards of 

 the metacyclic trypanosomes while the leech feeds. To this category 

 belong T. ahramidis, T. remaki, T. barbi, T. percce, T. acerincB, and 

 T. squalii. 



II. The trypanosomes develop in the stomach and then pass into the 

 intestine, where the flagellates persist. Before the leeches become infective 

 the intestinal forms reinfect the stomach, from which the proboscis sheath 

 is infected with metacyclic trypanosomes. To this group belong T. granu- 

 losum, T. danilewskyi, T. phoxini, and T. carassii. 



In the case of other trypanosomes, only part of the cycle was observed. 

 A development in the stomach was followed, but the subsequent events 

 were not traced. To this group belong T. barbatulce, T. langeroni, T . scar- 

 dinii, T. leucisci, and T. elegans. Tanabe (1924) has noted that the 

 trypanosome of the Japanese loach {Misgurnus anguillicaudatus) multiplies 

 for a period of three or four days in the intestine of the leech {Hirudo 

 nipponica). No transmission experiments were carried out. 



1. Large form in blood of skate. 

 2-10. Rounded forms from the alimentary tract of the skate. Some of these are without flagella, 

 and most of them are in process of division. 

 11. Crithidia form in crop of leech. 12-14. Trypanosome forms from crop of leech. 



15-16. Slender forms from the proboscis of the leech. 



