PROCESS OF REGENERATION 



107 



of their colored contents. The gradient of such an individual is 

 graphically depicted in text figure 2. In these graphs the ab- 

 scissae represent the number of segments and the ordinates, the 

 time of death in minutes. The dots along the curve are the 

 points actually determined experimentally. In text figure 2, 

 the flatness of the curve between the third and the fourth seg- 

 ments indicates that the head of a zooid is forming there; this 

 graph should therefore be compared with figure 1, which is the 

 disintegration gradient of a fully developed posterior zooid of 

 Aeolosoma, and which illustrates a typical primary gradient — 



1 2 



Fig. 1 The axial gradient of a mature zooid of Aeolosoma hemprichii, illus- 

 trating an ideal primary gradient. 



Fig. 2 The axial gradient of an individual Aeolosoma in which physiological 

 isolation of a zooid is beginning. 



i.e., one that is steepest at the anterior end, and gradually falls 

 off posteriorly. 



As the individual Aeolosoma grows, the posterior zooid con- 

 tinues to differentiate physiologically. When such an individual 

 is allowed to disintegrate in cyanide, the first change that occurs 

 is the appearance of a constriction near the posterior end. This 

 constriction marks the position of the head of the posterior zooid. 

 Disintegration then proceeds independently in both zooids, from 

 the anterior to the posterior end of each. Four stages in the 

 disintegration of such an individual are illustrated in figure 3, 



THE JOURNAL OF EXPERIMENT A.I, ZOOLOGY, VOL. 20, NO. 2 



