1916] CHILD—GRADIENTS IN ALGAE 
93 
physiologically isolated, and if the irritability gradient in its proto- 
plasm resulting from its former relations to the gradient persists, or 
if a new gradient arises in it, the reproduction of a new individual 
occurs. The space relations in the formation, inhibition, or de- 
velopment of buds in plants and the dominance of the chief growing 
tip seem to be fundamentally of this character. Growth in size 
of the plant or removal or inhibition of the chief growing tip results 
in physiological isolation of other parts, and new buds arise or buds 
previously inhibited develop. 
This in brief is the conception of physiological individuality 
which has developed from my experimental work on the lower 
animals. Since I have found metabolic gradients as character- 
istic features of the axes in animals and have been able to control 
and modify to a high degree size, development, and reproduction 
by controlling and modifying these gradients, it seemed desirable 
to determine whether the existence of similar gradients could be 
demonstrated in the simpler plants. The behavior in growth and 
development of the axis of the higher plant is a practical demonstra- 
tion of the presence of a metabolic gradient with the apical region 
as the region of highest rate, but I thought it of interest to apply to 
some of the simple plants methods which I had used for the simple 
animals. 
Methods and material 
In the course of experimentation on the lower animals, I have 
found that certain relations exist between metabolic condition and 
susceptibility to at least many agents and conditions which inter- 
fere with, depress, or inhibit metabolism in some way. These 
relations are briefly as follows: To agents and conditions which 
affect the organism in sufficient degree to bring about death in a 
short time without permitting adaptation or acclimation, suscepti- 
bility varies directly with metabolic rate or with the rate of certain 
undamental metabolic reactions, probably primarily the oxidations. 
The higher the rate of reaction the sooner death occurs, and vice 
versa. To agents and conditions which affect the organism to so 
slight a degree that more or less adaptation or acclimation is 
* For more extended consideration of the subject see: Cuitp, C. M., 1-4, 6, 7, 
9-11 (chapter ix), 12. 
