14 PRESIDENT’S ADDRESS. 
admit of numerical specification and prediction to a surprising extent; 
while modification by continuous variation, which seemed to be of the 
essence of Darwinism, gives place to, or at least is accompanied by, 
mutation, with finite and considerable and in appearance discontinuous 
change. 
So far from Nature not making jumps, it becomes doubtful if she 
does anything else. Her hitherto placid course, more closely examined, 
is beginning to look like a kind of steeplechase. 
Yet undoubtedly Continuity is the backbone of evolution, as taught 
by all biologists—no artificial boundaries or demarcations between 
species—a continuous chain of heredity from far below the amceba up 
to man. Actual continuity of undying germ-plasm, running through all 
generations, is taught likewise; though a strange discontinuity between 
this persistent element and its successive accessory body-plasms—a dis- 
continuity which would convert individual organisms into mere tem- 
porary accretions or excretions, with no power of influencing or con- 
veying experience to their generating cells—is advocated by one school. 
Discontinuity does not fail to exercise fascination even in pure 
Mathematics. Curves are invented which have no tangent or differ- 
‘ential coefficient, curves which consist of a succession of dots or of 
twists; and the theory of commensurable numbers seems to be exerting 
a dominance over philosophic mathematical thought as well as over 
physical problems. 
And not only these fairly accepted results are prominent, but some 
more difficult and unexpected theses in the same direction are being 
propounded, and the atomic character of Energy is advocated. We had 
hoped to be honoured by the presence of Professor Planck, whose theory 
of the quantum, or indivisible unit or atom of energy, excites the 
greatest interest, and by some is thought to hold the field. 
Then again Radiation is showing signs of becoming atomic or dis- 
continuous. The corpuscular theory of radiation is by no means so 
dead as in my youth we thought it was. Some radiation is certainly 
corpuscular, and even the etherial kind shows indications, which may 
be misleading, that it is spotty, or locally concentrated into points, as 
if the wave-front consisted of detached specks or patches; or, as J. J. 
Thomson says, ‘the wave-front must be more analogous to bright 
specks on a dark ground than to a uniformly illuminated surface,’ thus 
suggesting that the Ether may be fibrous in structure, and that a wave 
runs along lines of electric force; as the genius of Faraday surmised 
might be possible in his ‘Thoughts on Ray Vibrations.’ Indeed 
Newton guessed something of the same kind, I fancy, when he super- 
posed ether-pulses on his ccrpuscles. 
Whatever be the truth in this matter, a discussion on Radiation, 
of extreme weight and interest, though likewise of great profundity and 
