THE AXIAL GRADIENTS IN HYDROZOA. 183 



w/5o; HC1, ra/isoo, m/5OOO; neutral red. With some concen- 

 tration of each of these agents positive results were obtained, 

 and crowding, keeping in closed dishes, and infrequent change of 

 water also gave positive results. 



In the experiments complexes, stocks or "colonies" lacking 

 only the holdfast, or large complexes of stems and branches with 

 a single cut surface at the basal end were used. These were 

 placed in finger bowls holding about 400 c.c. of the experimental 

 solution made up with well aerated sea water. When volatile 

 agents w r ere used the bowls were completely filled and covered 

 with glass plates excluding all air, or all except a small bubble. 

 Solutions were renewed daily or every two days, except in experi- 

 ments to determine the effects of less frequent change. And 

 finally, in some experiments the same concentration was contin- 

 ued throughout, in others the original concentration was replaced 

 by a lower one, or the animals were returned to water after a day 

 or two. 



The figures are semi-diagrammatic but are all drawn from 

 living specimens. Old stems, branches or thecse which are 

 empty because of disintegration or resorption of hydranths or 

 retraction of ccenosarc are drawn in broken lines (Figs. 13-16, 

 1 8). Figs. 1-9, ii, 13 representing the development of stolons 

 in earlier stages of experiment are drawn in outline without in- 

 dication of ccenosarc, because all parts of stems and stolons 

 contain it. In the other figures the ccenosarc is indicated by 

 shading in order to show the later development and separation 

 of stolons from the stock. 



The chief purpose of the paper is the presentation of experi- 

 mental data w T hich show that transformation of stems and even 

 of apical regions into stolons may occur under slightly inhibiting 

 or depressing conditions. Questions of the range of effective 

 concentrations, of regional, individual, specific and experiment- 

 ally induced differences in susceptibility, and of the rate and 

 degree of transformation are considered only incidentally or not 

 at all. 



TRANSFORMATION IN Bougainvillea. 



Transformation of apical ends of branches into stolons often 

 occurs in nature in Bougainvillea. In freshly collected stocks 

 stolons are often found in place of some or all hydranths and 



