1893. NATURAL SELECTION AND LAMARCKISM. 339 
forehead, and nearly twice as often as the palm of the hand?3 Is it 
probable that the palm of the hand touches objects so much less 
frequently than the immediately adjacent finger joints as to account 
for its possessing little more than half their perceptiveness? Is the 
cheek touched twice as often or twice as impressively as the forehead, 
and nearly three times as often as the back of the hand? Mr. 
Spencer’s hypothesis does not seem to offer any assistance in ex- 
plaining the facts. While it can be reconciled with them in some 
respects, it is in direct conflict with them in others. All it can do, 
indeed, is partly to explain such facts as are already explicable by 
the natural selection of useful tactile powers. Nothing is gained by 
the introduction of the Lamarckian factor, which, accordingly, still 
remains as unproven as before. 
Mr. spencer’s explanation rests upon the probably correct 
opinion that tactile sensibility slightly increases with use, and upon 
the theory that acquired characters are transmitted to posterity. 
Now, the greatly increased tactile perceptiveness found in various 
parts evidently depends, as Mr. Spencer fully recognises, on an in- 
creased number of tactile areas possessing distinct and separate 
communications with corresponding sensation tracts or stations in the 
brain. Mr. Spencer urges, not merely that practice makes perfect, 
which would be a legitimate conclusion, but that it actually multiplies 
the lines of communication with distinct endings or areas in the skin and 
in the brain. Foster, however, whose authority in matters of physio- 
logy is at least as great as Mr. Spencer’s, tells us that ‘‘ The im- 
provement by exercise of the sense of touch must be explained, not 
by an increased development of the terminal organs, not by a 
growth of new nerve-fibres in the skin, but by a more exact limitation 
of the sensational areas in the brain” (Text-Book of Physiology, 
PP- 532, 533, third edition). If Foster is right, how could extreme per- 
ceptiveness be evolved by the inheritance of a slightly-improved 
limitation or clearer definition of the’ partially confused and inter- 
mingled areas of sensation? How could the transmission of a more 
perfect working order explain the formation of large numbers of fresh 
nerve-fibres provided with fresh sensational organs in the brain, and 
ending in the skin in corresponding tactile areas which, in the end of 
the forefinger, must be some goo times, and in the tip of the tongue 
some 3,600 times, as small and numerous as in an equal area in the 
back of the neck? It has always been supposed that increased use 
caused increased size. In this case it is conveniently, though incon- 
sistently, supposed to produce the opposite effect. The more a tactile 
area is used the smaller it becomes, until these areas are as minute 
5 If we hold that the discriminative sensibility of the tip of the nose is 
inherited from ancestral lemurs, which habitually applied the nose to objects 
as an organ of touch as well as of smell, then the long-continued retention of such 
seldom-exercised perceptiveness shows that the inherited effects of disuse have been 
so exceedingly slow and slight as to be altogether problematical. 
Z2 
