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covers decrease in bulk due to development and use as well as in- 
crease. 
When one passes beyond this and attempts to deal with the char- 
acteristics of ontogeny or phylogeny he at once finds himself in the 
presence of other forces, such as heredity and other processes, 
namely, the acquisition of new characters and the renewal of the 
powers of growth in nuclear substances by means of conjugation. 
The manifestation of growth energy, in brief, arises from two 
factors, or, at any rate, is always found associated with two, a living 
organism and assimilation of nutritive matter, and is an obvious 
result of their union. 
GENESIOLOGY. 
The term heredity has been used in two senses, one expressing 
the results of the action of an unknown force which guides the 
genesis of one organism from another and a second in which it 
implies the force itself. Clearness of statement demands that some 
other term than heredity should be used, and I have consequently 
proposed to designate the study of the phenomena by the term 
Genesiology, from I'fveors, meaning that which: is derived from 
birth or descent, this force itself as genetic force, and the principle 
of heredity thus becomes genism. 
The continuity of the same element in the agamic division of 
unicellular bodies, as in Protozoa, makes it comparatively easy to 
explain the transmission of likeness, but this is growth of the onto- 
genic cycle. Maupas shows this clearly and continually speaks of 
the growth, full-grown virility, and senility of his generations of 
unicellular, agamic protozoans. In fact they are obviously in a 
disunited form the equivalent of the colony of protozoans, and 
secondarily, although more remotely, the equivalent of the single 
metazoan, or individual, which is essentially a cycle of agamic cells 
reproducing by fission. 
While this likeness of agamic daughter cells to the original agamic 
mother cell which has disappeared in them may be considered a 
manifestation of heredity, it is also a form of growth and readily 
separable from the more complicated relations of organism pro- 
duced by conjugation of two forms. When the transmission of 
likeness is complicated with the effects of conjugation the difficul- 
ties increase until finally, in the bodies of the Metazoa, they culmi- 
nate in a problem of surpassing difficulty. Heredity is as plainly 
