500 T. H. Morgan. 



If the rate of development of the aboral hydranths depends, to 

 any extent, on the amount of fluid in the circulation, the A-pieces 

 should develop first, then the B-pieces, and lastly the C-pieces; 

 for the amount of gastro-vascular fluid, v^^ith its contained 

 material shut off^ in the basal end is greater in (A) than in (B), and 

 greater in (B) than in (C). The results show that in most cases 

 the order is that just given. 



In the first set tied after six hours, the rate in (A), (B) and (C) 

 seemed to be about the same. In the second set, tied after tvi^elve 

 hours, the (A) and (B) appeared at nearly the same time, but the 

 C-pieces w^ere distinctly delayed. 



In the third set, tied after six hours, the A-pieces developed 

 ahead of the (C's). There were no B-pieces. 



In the fourth set, tied after six hours, the (A's) developed before 

 the (B's), and the latter sooner than the (C's). (The diff'erence 

 between the (B's) and the (C's) was not marked.) 



In the fifth set, tied after six hours, the (A's) averaged better 

 than the (B's), and the (B's) better than the (C's), although the 

 diff^erence was more apparent at first than later. 



In the sixth set, tied after six hours, the (A's) began to develop 

 before the (C's). There were no B-pieces. The same difi^erence 

 could be seen throughout the later development. 



The results from these experiments all point in the same direc- 

 tion. The nearer the ligature to the basal end, after the oral end 

 had been allowed to develop for six hours, the later the develop- 

 ment of the aboral hydranth. Nevertheless without further 

 experiments I feel it unsafe to rely too much on these data, 

 because here also diff^erent pieces have to be compared, but if 

 the results are established by further work they indicate that the 

 materials of the circulation are a factor in the rate of aboral 

 development. It should be clearly understood that whether this 

 is true or not the general theory of polarity here proposed is little 

 affected, for the question of the rate of aboral development in a 

 piece tied at the oral end has only an indirect bearing on the prob- 

 lem of polarity. Only the rate is aff'ected. The heteromorphosis 

 is due to the totipotence of the stem and the stimulus of the free 

 end. 



