DYNAMICS OF MORPHOGENESIS 



137 



cut in water and placed in KCN^^Vu^m. at the same temperature 

 as soon as the cutting of the series was completed. Each lot of 

 both the control and the KCN was kept in a liter Erlenmeyer 

 flask filled with liquid except for a small air-space at the top, 

 and corked. The KCN solution was renewed every two days and 

 for the sake of uniformity the water of the controls was also 

 changed as the same time. The KCN-pieces remained in the 

 cyanide from November 28 until December 11 and were then 

 rinsed and placed in water. All pieces were examined December 

 19 to 21. The results, so far as they concern the character of the 

 anterior end, appear in table 5. 7 is the control in water, II the 



pieces in cyanide. The results are given in percentages which are 

 in all cases exactly double the actual number of pieces. 



In the first place, the control pieces show the usual axial gradi- 

 ent described in the first paper of this series (Child, '11 c). In 

 la 84 per cent are normal, 16 per cent teratophthalmic, a total of 

 100 per cent with eyes; in Ih only 10 per cent are normal and 72 

 per cent teratophthalmic, a total of 82 per cent with eyes; in Ic 

 10 per cent are normal, 28 per cent teratophthalmic and 2 per 

 cent teratomorphic, a total of 40 per cent with eyes. The 10 

 per cent of normal heads in Ic represents those cases in which Ic 

 contained a considerable portion of the second zooid. Pieces of 

 this length which are entirely from the posterior region of the 

 first zooid never produce normal heads under the conditions of 

 this series. 



