146 C. M. CHILD 



Table 8 gives the percentages. la-If are the controls and Ila- 

 Ilf the KCN-pieces. 



A comparison of the controls in table 8 with those of table 7 

 (p. 144) gives some idea of the degree of uniformity of the results 

 in parallel series. The worms for the two series were taken from 

 the same stock about two weeks apart. A comparison of the two 

 tables shows that the percentages are almost the same in both in 

 the pieces a, b, e and /, while pieces c and d show differences of 

 about 25 per cent in the two tables. These differences in c and 

 d are correlated with the presence of the second zooid. Slight 

 differences in the levels of the cuts in relation to the boundaries 

 of the zooids account for all such differences. If my series con- 

 sisted of much larger numbers of pieces these differences would be 

 much less, but it is impossible to take two sets of fifty worms 

 each, of approximately the same length and cut them into six 

 pieces so that the levels of the cuts shall stand in the same mean 

 relation to the boundaries of the zooids in each set. The similar- 

 ity of the other percentages in the controls shows, however, the 

 value of the method in regions where an invisible and uncon- 

 trollable factor is not involved. 



In the present series the effect of the KCN on the character of 

 regulation is different in certain respects from that in series 512 

 above. In I la a slight decrease in the frequency of normal forms 

 appears, as compared with the control la. The //6-pieces show 

 a slight increase in regulatory capacity over Ih and the pieces 

 lie, lid, lie show a great increase over the controls. In the /- 

 pieces the influence of KCN does not appear at all in the character 

 of regulation, though of course the rate in /// is much less than 

 that in //. No increase is possible here since the control shows 

 100 per cent of normal forms, so that all that we can say con- 

 cerning the effect of the KCN on these pieces is that it does not 

 decrease their regulatory capacity. In all probability its phy- 

 siological effect is similar to that on the d- and e-pieces, but does 

 not appear morphologically. 



This series affords a good contrast with the preceding. Here 

 the whole worms were placed in KCN before cutting, were cut in 

 KCN and remained in KCN forty-eight hours: here the effect of 



