Professor Henri Bergson’s Biology. 85 
Echinoderms and Molluses yield the road to the Arthropods and Vertebrates 
just as armour-clad knights had to give place to free-moving infantry men. 
Suppleness means success. 
When we look broadly at Arthropods and Vertebrates which have 
achieved similar successes on entirely different lines, we see that one thing 
they have in common is the high development of the sensori-motor system. 
That is the essential prize, all the rest is trimmings. Plants having gone 
predominantly into the business of making explosives and having made an 
inimitable success of it, it was the problem of animals to utilise these 
explosives effectively. And this is the business of the sensori-motor system. 
On it everything converges, the other functions are quite subsidiary. When 
“nervous activity emerged from the protoplasmic mass in which it was almost 
drowned, it had to summon around itself activities of all kinds for its 
support,” but they are the slaves, it is the master. Hence the index of 
evolution is in brains. 
Looking at the whole set of facts from a still greater distance, we see 
that the trend of animal evolution is towards freedom. The physical world 
has only determinate reactions, it 1s a realm of fatality, in which we always 
know where we are. The expected happens monotonously. But in the 
animate world there are alternatives and unforeseeabilities. We see 
spontaneity even when an Amoeba goes on the hunt, as it certainly does. 
“ At the root of life,” Bergson says, “there is an effort to engraft on to the 
necessity of physical forces the largest possible amount of indetermination.” 
And this it is that gives the nervous system its paramount interest that it 
is “a veritable reservoir of indetermination.” The main energy of the 
vital impetus has been spent in creating apparatus of this sort. 
THE RELATION BETWEEN INSTINCT AND INTELLIGENCE. 
Referring to the two great highways of animal evolution—Arthropod and 
Vertebrate—Bergson points out that two powers, immanent in life and 
originally intermingled, had here to part company. These are instinct and 
intelligence, the former finding highest expression in the ants and bees, the 
latter in man. SBergson’s view is that instinct and intelligence are on quite 
different tacks of evolution, and his theory of knowledge is closely bound up 
with this part of his theory of life. The problem of instinct is one of the 
major problems of biology, and many years of experiments like Lloyd 
Morgan’s will be necessary before we can decide between the various views 
recently discussed before the British Psychological Society. Bergson’s 
interpretation is one of several, and it must suffice to say that it has some of 
the quality which William James called “tough.” This is plain when we 
