LIFE HISTORY OF TWO RARE CILIATES 363 



On June 17, the cultures were carried in small phials from 

 New York to Maine. There was no opportunity to examine 

 them again until June 19 when it was found that all except 

 four individuals had encj^sted and all efforts to force them to 

 emerge from the cysts were fruitless. The four surviving indi- 

 viduals were normal in appearance and continued to divide. 

 On July 2, the culture was in a flourishing condition when without 

 any apparent cause, abnormal forms appeared, many died, 

 while among the surviving individuals the division rate was 

 practically nil. Various stimulants which previously had pro- 

 duced beneficial results, as for example, beef-extract, spring 

 water, ^, y^, ^-^oo solutions of KCl had no effect. On July 

 6, six individuals only remained, all of which were abnormal 

 (figs 6, 7, 8). On July 7, three of these encysted, the remaining 

 three disintegrating while under observation. During the re- 

 mainder of the month many unsuccessful attempts were made 

 to recover the encysted individuals and the race died out in 

 the 218th generation. 



7. Regeneration 



A few experiments were made to test the regenerating power 

 of Spathidium, but as these were limited in number and scope, 

 no general conclusions can be drawn from them. 



1. At 11.15 in the morning, half-an-hour after division, a 

 Spathidium was transferred to a depression slide, placed upoii 

 the stage of the microscope. With a sharp scalpel an incision 

 was made at right angles to the long axis of the body as near 

 the middle line as possible (fig. 32). The anterior half formed 

 a new vacuole, swam slowly about and at 12.15 encysted. The 

 posterior fragment rounded up, gradually elongated and assumed 

 normal shape. It was transferred at 12.15 p.m. and although 

 it swam actively about, coming in contact constantly with its 

 prey, no paralysis of Colpidium resulted. It would appear 

 therefore that either the trichocysts were functionless or had 

 not yet been formed. If Mitrophanow's theory of the nuclear 

 origin of these bodies be correct it seems resonable to believe 

 that sufficient time had not elapsed since the cutting for the 



