488 TRANSACTIONS OF SECTION D. 
bottom of his heart he knows he will never find, and yet the pursuit of 
which is his one-abiding interest. Had Frank Balfour lived we should, I 
think, have sooner returned to the broader lines of research as practised 
by Darwin, for it was his intention to turn himself to the physiology—using 
the term in its widest sense—of the lower animals. Towards the end of 
the nineteenth century, stimulated by Galton, Weldon began those series 
of measurements and observations which have culminated in the establish- 
ment, under the guidance of his friend and fellow-worker, Karl Pearson, 
of a great school of eugenics and statistics in London. With the beginning 
of the twentieth century came the rediscovery of Mendel’s facts, and with 
that an immediate and enormous outburst of enthusiasm and of work. 
Mendel has placed a new instrument in the hand of the breeder, an 
instrument which, when he has learnt to use it, will give him a power over 
all domesticated animals and cultivated crops undreamt of before. We are 
getting a new insight into the working of heredity and we are acquiring a 
new conception of the individual. The few years which have elapsed since 
men’s attention was redirected to the principles first enunciated by the 
Abbot of Briinn have seen a great school of genetics arise at Cambridge 
under the stimulating energy of Bateson, and an immense amount of work 
has also been done in France, Holland, Austria, and especially in the 
United States. As the work has advanced, new ideas have arisen and 
earlier formed ones have had to be abandoned; this must be so with every 
advancing science ; but it has now become clear that mutations occur and 
exist especially in cultivated species, and that they breed true seems now 
to be established. In wild species also they undoubtedly occur, but whether 
they are so common (in uncultivated species) remains to be seen. If they 
are not, in my opinion a most profitable line of research would be to 
endeavour to determine what factor exists in cultivation which stimulates 
mutation. 
To what extent Darwin’s writings would have been modified had 
Mendel’s work come into his hands we can never know. He carefully 
considered the question of mutation, or, as they called it then, saltation, 
and as time went on he attached less and less importance to these variations 
as factors in the origin of species. Ray Lankester has recently reminded 
us that Darwin’s disciple and expounder, Huxley, ‘clung to a little heresy 
of his own as to the occurrence of evolution by saltatory variation,’ and 
there must have been frequent and prolonged discussion on the point. That 
‘little heresy’ has now become the orthodoxy of a number of eager 
and thoughtful workers who are at times rather aggressive in their 
attacks on the supporters of the old creed. ‘That mutations occur and 
exist is obvious to everyone, but that they are of frequent occurrence 
under purely natural conditions is,’ Sir William Thiselton-Dyer 
thinks, ‘unsupported by evidence.’ The delicate adjustment between 
an organism and its natural surroundings suggests that sudden change 
of a marked kind would lead to the extinction of the mutating 
individual. As far as I can understand the matter in dispute, 
Darwin and his followers held that evolution had proceeded by small steps, 
for which we may accept de Vries’ term fluctuations; whilst the Muta- 
tionists hold that it has advanced by large ones, or mutations. But it is 
acknowledged that mutations are not all of the same magnitude, some, 
e.g., albinism ; brachydactyly in man ; dwarf habit or glabrousness in plants 
may be large; others, e.g., certain differences in shade of colour or in 
size, are insignificant, and indeed Punnett has suggested that under the 
head of fluctuating variation we are dealing with two distinct phenomena. 
He holds that ‘ some of the so-called fluctuations are in reality mutations, 
whilst others are due to environmental influence.’ He thinks the evidence 
that these latter are transmitted is slender, and later states that ‘ Evolu- 
tion takes place through the action of selection on these mutations. Where 
