TRYPANOSOMES OF AMPHIBIA 



593 



experiments with the tortoise and goldfish gave only negative results. 

 It is possible that T. rotatorium. occurs in a number of different hosts. 



Transmission.— The intermediate host of T. rotatorium, as first demon- 

 strated by Fran9a (1908a), and then by Noller (19136), is the leech, Hemi- 

 clepsis marginafa (Fig. 240), but before discussing the development in this 

 invertebrate it will be necessary to describe some details of its anatomy. 

 The mouth opens into the proboscis, a thick-ridged cylinder which is 

 armed with teeth, and completely retractable into 

 the proboscis sheath (Fig. 244). The sheath is an ^^ 



infolding of the anterior end of the body, forming &, 



a cavity in which the proboscis lies. Through the g^ 



anterior opening of the proboscis sheath the proboscis ^\ 



can be protruded at the time of feeding, while the rM 



margin of the proboscis sheath is applied to the skin. 

 It will thus be seen that in the act of feeding the 

 contents of the proboscis sheath can gain easy access 

 to the wound made by the proboscis. An oesophagus 

 leads from the proboscis to the stomach or crop, 

 a large structure with lateral diverticula occupying 

 most of the body cavity. From the stomach an 

 intestine with diverticula at its anterior end leads to 

 the anus. 



On account of the scanty infection in the tadpole, 

 it was impossible to observe the earliest stage of 

 development in the leech. In two or three days after 

 feeding on the infected tadpole there are present in 

 the stomach stumpy forms which were described as 

 having the leptomonas structure, but which may in 

 reality be crithidia (Fig. 239, 3). 



How these actually arise was not determined. 

 They may have been the result of repeated binary 

 fissions of the ingested trypanosomes, or, perhaps, 

 what is more probable, the products of the seg- 

 mentation of a spherical stage such as Robertson 



(1907, 1909, 1909r/) and Brumpt (1905) have described in the development 

 of fish trypanosomes in leeches (see p. (J03). Noller has observed such 

 a multiplication of the large thick individuals in cultures made from frog's 

 blood (Fig. 239, 8-10). From the third day onwards there begin to appear 

 very active narrow crithidia forms. At the end of a week narrow trypano- 

 somes occur, and they gradually replace the other forms (Fig. 239, 4-7). 



Towards the end of the period of digestion (ten to fourteen days) the 

 trypanosomes migrate forwards to the proboscis, and pass out of the mouth 



T. 38 



Fig. 240. — Hemiclep- 

 sis marginata, A 

 Transmitter of 

 Trypanosomes of 

 Frogs and Fish 

 ( X 3). (After 

 Harding, 1910.) 



