16 The Gemmule vs. the Plastidule as the [ January, 
as immediately active causes in the differentiation of the modes 
of molecular activity. Accordingly by the persistence of the 
type of molecular motion or motion of the plastidule, its charac- 
teristics tend to be exactly reproduced where reproduction is a 
process of mere division, as in the Protista. On the other hand, 
the motion of plastidule tends to vary as the surrounding condi- 
tions vary. Hence the difference in individuals arising from this 
adaptive power of the plastidule to accommodate its motions to 
the environment. Where the process of reproduction is sexual 
the fusion or blending of the products of the sex-glands to form 
embryos, there results a blending of the plastidular motion of the 
two. The characteristics of the resulting being is hence a result- 
ant of two molecular modes of motion in the same way as the 
diagonal of a parallelogram of forces is the resultant of two more 
or less antagonistic forces. Putting this and that together, it is 
clear in what manner the characteristics of the offspring of sexual _ 
unions may come to preponderate in favor of the one or the other 
_ parent as the plastidular-molecular motion of the germ elements 
preponderates over that of the sperm element, and vice versa, 
thus mutually modifying each other in order to produce a result- 
ant. It is also conceivable that the plastidular motions of remote _ 
ancestors as well as of approximal ones, tending to be persistent, 
may suddenly re-appear under favorable conditions, and that in 
this way there may arise a tendency to revert to such ancient 
progenitor. This hypothesis, if extended so as to conceive 
of the molecular vibrations of different stages of develop- 
ment as composing parts of a great molecular rhythm 
coeval with the first appearance of life on the earth, also 3 
explains the phenomenon of the recapitulation of Phy/ogeny and 
ontogeny. The tendency is to manifest the molecular motions 
in the order in which they succeeded each other in time. The 
registry or repetition in ontogeny being not always exact, it may 
-~ be assumed that in the process of differentiation some of the page A 
of vibration were in these instances irrecoverably lost. 
- Stated thus briefly, it seems to me unnecessary to enter into the _ 
account of the hypothesis of perigenesis further than to impress upon 
the mind of the reader that the vibrations of the plastidules are | 
_ adaptive in character, that is, they are the resultants of outward con- Ei 
_ ditions, represented hypothetically by X or any other unknown, ; 
> static or dynamic quantity. The theory is therefore purely me- 5 
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