290 THE ORCHID REVIEW. [OcroBerR, 1908, 
organism in the world must depend partly at least on its being highly 
sensitive to changes in its surroundings. It was the adaptive side of the 
fact that living protoplasm is a highly unstable body. From the Darwinian 
standpoint it would be a remarkable fact if the reactions of stimuli were not 
adaptive. 
The reaction of an organism depends on its past history, and in the 
higher organisms past experience is all-important in deciding the nature of 
response to stimulus. Morphological changes and the stimuli by which 
they are produced have now been brought under the rubric of reaction 
to stimuli. It is now widely believed that the nucleus is the. bearer 
of the qualities transmitted from generation to generation, and the regulator 
of ontogeny, and it may play the part of a central nervous system. 
Although plants had no nervous system, the complex system of nuclei 
connected by protoplasmic threads, might play the part of nerves. 
Among habits illustrating a mnemic or memory-like factor in the life of 
plants might be mentioned the habit of sleeping. Sleeping plants had a day 
position and a night position, but if a plant in a sleeping position were 
placed in a darkened room, it would be found next morning in the light 
position, even if all light were excluded. The habit had been built up by the 
alternation of day and night, and the leaves now rise and fall in the absence 
of the original stimulus, a capacity acquired by repetition. Buta rhythm of 
six hours or of a much shorter period could be built up artificially. When 
a series of actions follow each other in natural sequence, they become 
organically tied together, or associated, and follow each other automatically, 
even when the whole series of stimuli are not acting. 
As regards reaction to environment, a plant anda man must be placed 
in the same great class, in spite of their enormous differences. He believed 
that the mnemic quality in all living things must depend on the physical 
changes in protoplasm, and_ therefore it was permissible to use these 
changes as a notation in which the phenomena of habit might be expressed. 
Morphological changes were reactions to stimulations of the same kind 
as the temporary changes already discussed, and here indeed were the most 
striking cases of habit to be found. The development of the individual from 
the germ was by a series of stages of cell division and growth, each serving 
as a stimulus to the next, and each following its predecessor like the move- 
ments linked together in an habitual action performed by an animal. The 
rhythm of ontogeny is actually and literally a habit, and has all the charac- 
he same—an automatic quality which is seen in the 
performance of a series of actions in the absence of the complete series of 
stimuli to which they were originally due 
is all bisexual organisms the ontogenic rhythm of the offspring is a 
combination of the thythms of its parents, and in Crossing the result may 
