XIV 
FUNDAMENTAL FROBLEMS 
437 
by the action of the fundamental laws of growth. Admitting 
that such laws have determined some of the main divisions of 
the animal and vegetable kingdom, have originated certain 
important organs, and have been the fundamental cause of 
certain lines of development, yet at every step of the process 
these laws must have acted in entire subordination to the law of 
natural selection. INo modification thus initiated could have 
advanced a single step, unless it were, on the whole, a useful 
modification ; while its entire future course would be necessarily 
subject to the laws of variation and selection, by which it 
would be sometimes checked, sometimes hastened on, sometimes 
diverted to one purpose, sometimes to another, according as the 
needs of the organism, under the special conditions of its 
existence, required such modification. We need not deny that 
such laws and influences may have acted in the manner 
suggested, but what we do deny is that they could possibly 
escape from the ever-present and all-powerful modifying effects 
of variation and natural selection. 1 
Weismann’s Theory of Heredity. 
Professor August Weismann has put forth a new theory of 
heredity founded upon the “ continuity of the germ-plasm,” 
one of the logical consequences of which is, that acquired 
characters of whatever kind are not transmitted from parent to 
offspring. As this is a matter of vital importance to the theory 
of natural selection, and as, if well founded, it strikes away the 
foundations of most of the theories discussed in the present 
chapter, a brief outline of Weismann’s views must be attempted, 
1 In an essay on “The Duration of Life,” forming part of the translation 
of Dr. Weismann’s papers already referred to, the author still further 
extends the sphere of natural selection by showing that the average duration 
of life in each species has been determined by it. A certain length of life is 
essential in order that the species may produce offspring sufficient to ensure 
its continuance under the most unfavourable conditions ; and it is shown that 
the remarkable inequalities of longevity in different species and groups may 
be thus accounted for. Yet more, the occurrence of death in the higher 
organisms, in place of the continued survival of the unicellular organisms how¬ 
ever much they may increase by subdivision, may be traced to the same great 
law of utility for the race and survival of the fittest. The whole essay is of 
exceeding interest, and will repay a careful perusal. A similar idea occurred 
to the present writer about twenty years back, and was briefly noted down at 
the time, but subsequently forgotten. 
