268 JouURNAL OF COMPARATIVE NEUROLOGY. 
invasions, floods and drought; earthquakes, volcanoes and land- 
slides; the submersion and elevation of continents and islands; 
the drying up of inland seas; changes of ocean and air currents; 
in short, any catastrophic or cataclysmic changes in nature. 
And to such abrupt general changes we must add all sorts of 
chemical agents, physical strains and contacts, mechanical hin- 
drances or helps to growth, changes in light, moisture, temper- 
ature, etc. These are only a few of the many conditions that 
might be named which would give rise to the necessity of new 
adaptations on the part of organisms. It would be interesting 
to know in detail the steps by which certain land forms returned 
to an aquatic life, certain mammals took to burrowing in the 
earth and others to an arboreal life. What led tothe divergence 
of the birds and reptiles from a common stock? Why did the 
birds develop nidification and incubation and the mammals the 
placenta? How did animals first come to hibernate? What 
stress of conditions in the struggle for life led to the keen devel- 
opment of the sense of smell in the deer or the hound? Under 
the stress of what economic problems was fire first discovered 
or huts first built or clothing first worn ? 
It must be remembered that these problems were solved 
one by one in the evolution of consciousness. They did not 
come to the primitive consciousness in their ensemble as they 
appear to us. The chief objection that has been raised to the 
work of the recent experimental school of comparative psychol- 
ogists has been that the artificial conditions of the experiments 
interfere with the natural instincts and proclivities of the animal. 
The conditions of the experiments do not approximate the 
‘conditions to which the animal is subjected in the state of na- 
ture. Hence the conclusions based on observation of animals 
under such conditions are apt to be distorted. An animal can 
only be expected to exhibit what rationality it possesses when 
the problem to be solved lies in the line of its inherent abilities. 
It is not remarkable that an animal when placed in a situation 
which is almost wholly different from any of the typical situa- 
tions into which it is liable to be thrown in its natural state, 
should respond to that situation quite blindly and vaguely. The 
