184 BULLETIN OF THE UNITED STATES FISH COMMISSION. 



appeared to unite in a common wall. Whether they really united, however, or whether 

 the distance between them was so slight as not to be recognized (cf. fig. 8), I am of 

 course not able to say, as any attempts to demonstrate the true condition would have 

 destroyed the specimen for further observation. 



At 5:30 the cells had changed position slightly, but no further division had taken 

 place. 



By 7 :30 the 32-cell stage was reached, but it was impossible to follow the origin 

 of the various cells, as they changed position so rapidly. 



At 8:30 the membrane surrounding the small cells resulting from cell II (fig. 9) 

 broke, and all the young ciliates except three escaped. 



By 10 o'clock the cells of cyst I had undergone another division. I was able to 

 count 27 with certainty, and in all probability this represented a 32-cell stage of this 

 cyst (64-cell stage of the original animal), as several cases of doubtful division were 

 not included in the number 27. One of the cells remaining in cyst II had divided, 

 but the other two remained intact. 



At 11 p. m. another division had taken place in cyst I; the resulting cells were 

 about the size of the cells of the G4-cell stage, and this theoretically evidently repre- 

 sented a 64-cell stage of cyst I (128-cell stage Of the original animal), although the 

 young animals now revolved and changed place so rapidly that it was utterly impos- 

 sible to count them. Xo change was noticed in cyst II, or in the cells which had 

 escaped from cyst II and were swimming around in the preparation. 



At 12 m. no change had taken place, and the preparation remained the same until 

 1 :30 a. m., when it was placed aside for the night. 



At 11 a. m. nothing could be seen of cyst II; cyst I had broken, and its contents, 

 for the most part, had escaped, while the cells remaining in the cyst were dead. 



A number of other cases of division were observed, which were essentially the 

 same as the one just described. In many cases, however, it was impossible to follow 

 the origin of the various cells beyond the 8-cell stage, and considerable variation was 

 noticed in the time of the appearance of the surrounding membrane. The following 

 are some of the more important observations: 



Many of the ciliates become encysted while still on their hosts, and there undergo 

 a division. I have found cysts of the 1, 2, and 4 cell stage on the host, bnt never any 

 beyond this stage. [The hosts had been dead for several hours.] Many of the parasites 

 encyst themselves shortly after leaving their hosts before any division takes place. 



The first division may take place before any encystment, one cell swimming off and 

 apparently undergoing no farther division (for the time being, at any rate), while the 

 other cell remains quietly in its place, encysts itself and divides into numerous small 

 ciliates; or the first division may take place before any membrane appears, the two 

 cells may swim around independently of each other; each may then become encysted 

 and proceed to divide. 



So far as my observations go, the surrounding membrane may appear in or at the 

 end of the 1, 2, 4, or 8 cell stage. That is to say, I have observed these stages when, 

 so far as I could discover, there was no membrane present, but when the membrane would 

 gradually appear in the next succeeding (2, 4, 8, 10 cell) stage. I repeat, for emphasis, 

 that I did not attempt to prove the presence of a membrane by resorting to any 

 staining methods. 



