THE H^MOPLAGELLATES. 195 



The parasites free themselves from one another^ and the 

 rosette is dissolved. The entire set of phenomena also occurs 

 in the blood of the owl. Schaudinu ventures no conjectures 

 with regard to its biological significance. 



(d) The Behaviour and Subsequent Development of 

 the Trypanosomes in the Vertebrate Host. 



All the Trypanosomes met with in the blood of the owl are 

 easily recognised as belonging to one or other of the three 

 categories found in the gnat. Even though the parasites in 

 any given phase may not exactly agree in the two hosts so far 

 as minute detail is concerned^ a study of their previous and 

 subsequent history in both cases renders it, nevertheless, 

 manifest that the two forms are the homologues of each 

 other; and, in fact, in all essential characters the Trypano- 

 somes, as seen in the owl, agree with the corresponding 

 type in the gnat. One distinction Avhich may be noted 

 is the presence, in the former case, of pigment in the cyto- 

 plasm, produced as the result of the alteration of the hasmo- 

 globin of the red blood-corpuscles. 



(1) Indifferent Trypanosomes. — The larger forms 

 entering the blood continue to divide until the size of 

 their descendants is sufficiently reduced. The small ones 

 attach themselves directly to the erythrocytes, and enter 

 upon a period of rest and growth. The mode of attachment 

 has been described above (p. 171), and is shown in fig. 13 a. 

 The locomotor apparatus disappears, and the kinetonucleus 

 takes up a position in close contact with the trophonucleus 

 (b and c). The form of the body is now quite that of a 

 young Halteridium, and, after twenty-four hours, the 

 first pigment grains appear in the cytoplasm. By this 

 time the parasite has increased to about double its original 

 size. It now becomes vermiform and active, reconstitutes its 

 flagellum, etc., and leaves the host-cell (d), usually in the 



