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Proceedings of the Royal Society 
set of “ leaves ” should he added, and thus to fig. c there should he 
apposed another similar figure, yet divergent enough to express the 
difference between the sexes. The mode of representing the process 
of “alternation of generations,” already explained at p. 918, will 
readily suggest itself. 
In short, then, when the genealogical tree has thus been magnified 
until we can study the succession of organisms which compose it, we 
find that the explanation of the morphological and physiological 
phenomena which this succession presents and involves ( i.e ., those 
of growth, reproduction, sex, and heredity) becomes raised from the 
plane of detailed, un-coordinated, and empirical observations and 
hypotheses, to that of a generalised and verified rationale or law , by 
the deductive application (which the historic survey of the preceding 
paper showed to be at once legitimate, urgent, and profitable) of 
that simple principle which is fundamental in biology. 
We thus come to understand the phenomena of heredity and 
growth, of reproduction and sex, as a continuous series of expressions 
of whole activities ;‘of the organism ; and thus the marvellous 
phenomena of sex are seen to he no isolated ones, but, in animal or 
plant alike, the highest outcome, the literal blossoming, of the 
individual life. 
At this point the present exposition naturally closes, since its 
obvious applications to the problems of human life cannot he 
entered on within the present paper. Yet a new and vaster deduc- 
tive application of the same principle must he indicated. Tor if the 
details of the genealogical tree he thus explained, so also may the 
curves, the general direction, nay, the very origin, of its branches ; 
i.e., the problem of those variations which we know as sexual, leads 
us to the problem of variations in general ; it enables us to look 
forward to the solution of the problem of aetiology in deeper terms 
than those of “ natural selection ” alone, as illustrations of a con- 
tinuous rhythm of anabolic and kataholic change.* 
NOTES. 
1. (P. 917.) A thoroughly parallel instance of the association 
between a specially anabolic environment and the non-occurrence of 
sexual reproduction is afforded by the recent observations of 
* See “ Yariation and Selection,” in forthcoming volume of Ency. Brit. 
