220 MISCELLANEOUS EXAMPLES 



accustomed to go through. And perhaps this might have been, in 

 pai-t, due to the fact that, three or four days before the date of my 

 first examination of the scum, I had put a glass cover over the jar, 

 and had consequently cut off the supply of fresh air. This 

 undoubtedly had a very injurious effect upon some of the 

 organisms on the sides of the vessel, as over the lower third there 

 were a number of small red worms in loose sheaths dihgently 

 devouring the scum before the cover was applied: but when I 

 began my examination I found some of these worms dead within 

 their sheaths, as well as very many of the latter empty, and not 

 a single one of them containing a living worm. 



Several different kinds of changes were seen taking place within 

 these encysted Prorodons which I have elsewhere described 

 (" Studies," pp. 20-24) ; but the particular transformations now to 

 be referred to were met with most frequently in portions of the scum 

 which, after having been scraped off the sides of the glass, were 

 subsequently kept for two or three days, previous to examination, 

 in such compressed or rolled-up masses in a small vessel containing 

 distilled water. Other specimens, however, have also been found 

 undergoing similar changes in portions of scum examined directly 

 after they had been removed from the walls of the tall glass vessel. 

 The commonest of the changes found was one by which the 

 entire contents of the cyst ultimately broke up into a number of 

 very coarsely granular spheres, each of which developed into a 

 Peranema. 



During the early stages of this change the encysted matter, as a 

 whole, loses its ordinary granular appearance ; it becomes more 

 refractive, and with what would be an approach to translucency 

 were it not closely studded with coarse, fatty-looking particles 

 (Fig. 40 ( X 350) C). Soon, traces of separation into distinct units 

 begin to show themselves as in D and E (x 250) and Fig. 41, A 

 (x 500). Later still, spherical bodies of variable size actually 

 separate from the parent mass ; so that the whole cyst may be seen 

 to be completely filled with a closely packed aggregate of motion- 

 less and coarsely granular spheres, as shown in Fig. 40, F. 



At other times the units that separate from the matrix may be of 

 fairly equal size and larger, but leaving a certain amount of uncon- 

 verted residual matter, as in Fig. 41, B (x 250). Here the units 

 not being so closely packed showed slow, semi- rotatory or pendulum- 

 like movements, and had to be killed with a weak formalin solution 

 before the photograph could be taken. In another cyst there were 



