674. JULIAN 8. HUXLEY 
In ordinary organic systems, therefore, we must recognize 
that we may have to deal with any of the following pheno- 
mena : 
(1) Physiological dominance and subordination of parts, 
manifesting itself first as regards conduction and control of 
asexual reproduction, secondly as regards nutrition. 
(2) Differential susceptibility. 
(3) Dedifferentiation. 
(4) Differential inhibiticn. 
(5) Resorption. 
(6) Reversal of dominance. 
Parallel phenomena occur in other organic systems in which 
parts are related in equilibrium. Thus dominance, subordina- 
tion, differential susceptibility and inhibition, a form of dediffer- 
entiation, and reversal of dominance, also occur in psycho- 
physical systems, both in some where consciousness is involved 
and in some where it is not, as will be dealt with more fully 
later. Here the dominance may be called neurological and 
psychological, and the dedifferentiation is of course unaccom- 
panied by-physical dedifferentiaticn of nerve-tissues. 
Many of the phenomena of inhibition, e. g. of buds by growing 
tips in plants, ard within the central nervous system, ebviously 
depend upon relations of dominance and subordination. A few 
examples will perhaps serve to illustrate some of these general 
statements. 
We may start with the example already referred to, of 
Stenostoma (Child, 1904), since here dominance and resorption 
are very Clearly shown. When a solitary Turbellarian is divided, 
regeneration of a head usually occurs from the anterior cut 
surface. In Stenostoma, however, which is a chain-forming 
organism, if a cut is made across the body of one of 
the central zooids, such regeneration from the anterior cut 
surface does not take place. Instead, the half-zocid which is 
attached to the anterior end of the posterior half-chain will 
shrink, assume a more rounded form, and eventually disappear 
altogether. 
Not only this, but the relative age of zooids determines 
