REVERSIBILITY OF MORPHOGENESIS 9 



larger end of figure 23a had become dominant. Seventy-two hours, one 

 oral groove, partly closed. Ninety-six hours, dead. 



Figure 23b. Twenty-four hours; heteromorphic (shown by ciliary 

 currents). A rudimentary mouth at each end, oral groove continu- 

 ous, nucleus present. The action of the cilia reminds one strongly 

 of the cilia of Paramecium when under the influence of a direct electric 

 current. Forty-eight hours, dead. 



Experiment 8. Forty individuals cut into anterior and posterior 

 halves. Two out of the 80 pieces became heteromorphic. At inter- 

 vals the regenerated pieces were fed protozoa from a wild culture not 

 containing Bursaria. This in part accounts for the long life of the 

 regenerated pieces. 



Figure 24. Six hours; almost fully regenerated. Twenty-four 

 hours; perfectly normal, and continued to remain normal up to ninety- 

 six hours. At one hundred and twenty hours it was abnormal, in 

 shape of a pyramid. One hundred and forty-four hours and one hun- 

 dred and sixty-eight hours still abnormal. One hundred and ninety- 

 two hours heteromorphic; drawn (fig. 24). At two hundred and six- 

 teen hours it was nearly normal, ciliary currents in same direction, 

 one gullet quite well differentiated. Two hundred and forty-eight 

 hours, dead. 



Figure 25. Six hours; regenerated to normal, twelve hours; perfectly 

 normal. Forty-eight hours; perfectly normal. Seventy-two hours; 

 normal but with a notch at posterior end. One hundred and twenty 

 hours, normal, large. At one hundred and ninety-two hours it had 

 divided into four; two of these were dedifferentiated, these were re- 

 moved from the watch glass. The other two formed an equal hetero- 

 morphic pair, drawn (fig. 25). Arcellae had been ingested by both 

 individuals of the heteromorph. Two hunderd and sixteen hours, two 

 separate, dedifferentiated individuals resulting from separation of 

 heteromorph. Two "hundred and forty hours, dead from starvation. 



Experiment 7b. Fifty cut crosswise into two equal anterior and 

 posterior halves. One out of the 100 pieces became heteromorphic. 



Figure 26. Twelve hours, partly dedifferentiated, oval, with spine 

 present. Twenty-four hours, heteromorphic, drawn (fig. 26). Fed 

 with other protozoa. Thirty-six hours, normal, spine had become 

 constricted off at base and the gullet at the base of the spine had 

 dedifferentiated and disappeared. The ciliary beat on the posterior 

 end was now reversed to agree with that of the larger end. Forty- 

 eight hours; perfectly normal; the free cytoplasmic piece formed from 

 the spine had no macronucleus, was active, but had decreased in 

 size. Sixty hours, perfectly normal, feeding. The detached spine was 

 small but active, not dedifferentiated. Seventy-two hours, perfectly nor 

 mal; detached spine dead. Eighty-four hours, dedifferentiated active 

 SDhere. Ninety-six hours, thick cyst. 



