250 



C. M. WENYON. 



glass cultures described above. Both the amoeboid and the 

 free-livino- forms divide in this manner, but on account of the 

 more sluggish movements of the former they are more readily 

 kept under observation. 



In the cultures encysted forms commence to appear after a 

 few days. In the liquid cultures they are to be found in the 

 .scum on the surface or in the deposit at the bottom. On the 

 agar cultures the cysts appear in the older parts of the culture. 

 On this medium the margin of bacterial gi-owths spreads over 

 the surface, and in this margin the actively reproducing 

 llao-ellates are to be sought. In the oldest part of the culture 

 no free flagellates can be found, but only the cyst. 



Text-fig. 6. 



Text-fig. 8. 



Encysted forms sliowin<^ refrae- Free form with refractile granules, 

 tile ft-ranules surrounding Prol)able preparation for en- 



niicleus. 



cystment. 



In the fresh condition these cysts appear as slightly brownish 

 spherical bodies, with a wall of double contour. 



At the centre of the cyst is the spherical nucleus, which 

 has similar characters to that of the free form, except for the 

 prolongation towards the flagella. The nucleus is surrounded 

 by the bright refractile granules, which were described as 

 occurring iu some of the free forms. It is probable these 

 granules are of a chromatin nature, and that they arise from 

 chromatin passed out from the nucleus, though this process 

 has not been followed. 



Though these organisms have been kept under observation 

 for a year or more conjugation has not been seen, nor has 

 any sexual process been detected. It is possible that some 

 sexual process is bound up with the encystment, but as the 



