1. The several growth-cycles which are distinguishable in the growth of an animal or plant are mutually independent in that they do not share a common catalyser.

2. The growth of the white mouse has been shown to consist of three autocatalytic processes and one "linear process" of weight-accretion. The parameters of these processes have been evaluated for one strain and generation of mice.

3. The first and most extensive autocatalytic process is asymmetrical, being defined by an equation of the type:

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The second and third cycles, which are more rapid and do not begin to affect the growth of the animal until a later stage of development, are symmetrical, being defined by equations of the type:

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4. The amplitude of the first autocatalytic growth-cycle in the mouse is almost the same in males and females, but the moment of maximum growth-velocity in the female anticipates that in the male, the velocity constant is smaller in the female, and the asymmetry estimated by the magnitude of the constant B, is greater in the female than in the male.

5. The amplitude of the second cycle is almost the same in males and females, but data are as yet lacking which would enable us to ascertain whether the velocity-constant and moments of maximum growth-velocity in this cycle differ in the two sexes or not.

6. The amplitude of the third cycle is much less in the female than in the male, and this difference of amplitude almost wholly accounts for the difference of adult weight in the two sexes. The velocity-constant of the third cycle is, however, greater in the female than in the male. Maximum growth velocity due to this cycle is attained at very nearly the same age in both sexes.

7. The origin of asymmetry in autocatalytic growth-processes is discussed. It is pointed out that asymmetry might originate in a progressive diminution of the velocity-constant. If this is the origin of the asymmetry of the first growth-cycle in the mouse, then it is shown that the velocity constant of autocatalysis in this cycle must be very nearly proportional to the nucleo-cytoplasmic ratio, as estimated by the chemical method of Le Breton and Schaeffer.

8. It is pointed out that no reliable measure of senescent loss of weight is available at present. It is shown that removal or decay of those conditions which initially maintain the separability of the growth-cycles which collectively constitute the growth of the white mouse would necessarily result in loss of weight.

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