PREVENTS ENCYSTMENT 10$ 



to such an extent that the whole stock was 

 purposely destroyed, and everything sterilised, 

 the experiments being continued with a fresh 

 culture. No trouble of this nature recurred for 

 some months, until one of us (J.W.C.), while 

 preparing pure mixed cultures, selected an area 

 from a plate consisting of free amcebse and a few 

 bacteria ; the subcultures from this did not appear 

 to be doing well, and on examination the same 

 unusual-looking bodies were found as before. 

 Efforts were made by diluting the cultures with 

 water to get the amcebse to encyst, so that the 

 parasite could be destroyed with some germicide, 

 but this measure had the opposite effect and all 

 the amcebse were killed. Eventually the almost 

 pure culture which we were so near obtaining had 

 to be discarded. 



In a large number of cultures of amceba infected 

 with this body we had not hitherto seen a single 

 cyst, but it has been found recently that encyst- 

 ment may occur after several weeks. By this 

 time the parasite has also ceased to grow, and 

 those amcebse which have so far escaped are able 

 to recover, and subsequently to multiply and 

 encyst. On transferring such cysts to a fresh 

 medium, the amcebse which escape, however, do 

 not look quite normal. In most of them the 

 nucleus has broken up into chromidia, and it is 

 a most striking fact that they now very frequently 

 multiply by budding into as many as a dozen 

 small amcebulse, the dividing amoebae exhibiting 

 a rosette-like appearance which is quite char- 

 acteristic. 



The " bodies " under consideration were not easy 



