CONCLUSIONS AND SUGGESTIONS 179 



opposite direction. If the latter attains a sufTicicntly 

 high rate it interferes with or obhterates the other and 

 the hydranth develops, though partial inhibition may 

 be evident in its shortness and slow development. 



In the case of a lateral bud of a plant, the develop- 

 ment of which is inhibited by the main growing tip, 

 the relation is probably the same. As long as the bud 

 is within the range of dominance of the growing tip its 

 own gradient from apex to base is more or less com- 

 pletely obliterated by a gradient from base to apex 

 determined by the main growing tip. This may in 

 time alter the protoplasmic gradient in the bud deter- 

 mined in the earlier stages of its individuation so that 

 it becomes incapable of development or develops only 

 into a short branch, a spine, or some other rudimentary 

 structure. It is interesting to note that Mogk in his 

 studies of plant correlation finds that when the axillary 

 shoots of a seedling are allowed to grow until they 

 attain dominance over the main shoot (see pp. 152, 153), 

 the latter often dies and the death gradient is in the 

 reverse direction from that of death from lack of water 

 or other conditions in an uninhibited shoot. Leaves 

 and roots probably represent partially inhibited gradi- 

 ents under certain conditions, and some of the specialized 

 outgrowths on the animal body, such as appendages, may 

 perhaps in some cases represent somewhat similar rela- 

 tions, though I know of no definite evidence bearing on 

 this point. 



So far as the evidence goes, it indicates that all 

 inhibition of this sort is a matter of interference between 

 gradients in opposite or nearly opposite directions, the 

 one gradient reducing, obhterating, or even reversing 



