Protozoan Studies 277 



time making their way with ease through the same zooglea at 

 least part of the wall of the cyst must be secreted by the Para- 

 mcecium. During the formation of the cyst the animal contin- 

 ually rotates inside of it and the cihary coat is never lost. The 

 cyst gradually contracts until it is shorter than the occupant, 

 which may have the anterior end folded over the middle of the 

 body or the ectoplasm thrown into folds. After the animal has 

 been in the cyst for some time the folding of the ectoplasm may 

 assume the character of an invagination of the anterior (rarely 

 posterior) end. The invaginated ectoplasm seems to be in large 

 measure absorbed, for after several days the occupant of such a 

 cyst looks like merely the posterior end of a Paramcecium. If the 

 cyst is opened or if one waits until the occupant comes out of its 

 own accord, the latter will swim about and ingest its food as 

 though an anterior end were superfluous. I found numbers of 

 Paramoecia without anterior ends, and a few without posterior 

 ends, in the old culture in which the encystment was found. One 

 of these is represented in Fig. 8, a. It was isolated in a watch 

 crystal and remained in the form of the figure two days. On the 

 third day it had changed to the form shown in Fig. 8, h. This 

 might be interpreted as a division in which the reduced vitahty 

 of the animal prevented the complete separation of the daughters, 

 followed by a partial division of one of the daughters. The speci- 

 men was lost so that its later history could not be followed. 



Some abnormalities seem to be the result of the plasticity of the 

 adoral side at the time of conjugation. A pair of conjugants were 

 isolated, and when they separated the adoral regions were drawn 

 out into prominences (Fig. 9). Such prominences are gradually 

 absorbed although they may remain for several days. These 

 prominences do not seem to be of the same nature as the horns 

 shown in Fig. 7 since so far as the investigations go the horns do 

 not and these smaller prominences do disappear. If Paramcecia 

 are shaken up with broken glass all those that are not killed or 

 cut in two regain their normal form in a short time (and even 

 fragments if they live regenerate after a longer period) although 

 they may be so torn and mashed out of shape as to bear httle 

 resemblance to the type. Probably the form of a Paramcecium 



