DYNAMICS OF MORPHOGENESIS 



145 



siological division of one. And finally the /-pieces of the control 

 are 100 per cent normal, a much higher percentage than in d or 

 e. Figure 46 shows that these pieces correspond approximately 

 to the most posterior zooid or series of short zooids and their 

 peculiar regulatory capacity is due to this fact. 



In the KCN pieces Ilia shows a slight decrease in normal forms 

 as compared with la, and 7/76 shows a much greater decrease in 

 head frequency as compared with 76. In c, d. e and /, on the 

 other hand, the KCN has practically no effect on the character of 

 the regulation, i.e., the posterior zooids are clearly distinguishable 

 from the posterior region of the anterior zooid by the difference 

 in their reaction to the KCN. 



Series 494 I and II. February 15 to March 3, 1912. Here, as in 

 the preceding series, the body is cut into six pieces of equal length 

 and regulation in water is compared with regulation in KCN 

 but the KCN is used in a different way. The worms for the KCN 

 lots were placed in KCN to o¥ot7o mfor three to five minutes before 

 being cut into pieces, the pieces were then cut in the same solution 

 and were placed at once in flasks which also contained KCN of the 

 same concentration: after forty-eight hours they were rinsed and 

 returned to water where they remained until regulation was com- 

 pleted. Lots of fifty pieces each were used. The controls con- 

 sisted of lots of fifty each in water at the same temperature. 



TABLE 8 



THE JOURNAL OF EXPERIMENTAL ZOOLOGY, VOL. 13, NO. 1 



