278 Animal Intelligence 
willingness to leave the eggs, showing that the disposition 
to remain over them is instinctive. If we start with forms 
of similar sedentary mode of life, it is easy to see that re- 
maining over the eggs would be the most likely thing to 
happen, even if no instinctive regard for them existed. 
The protection afforded would, however, be quite sufficient 
to insure the development of the instinct, natural selection 
favoring those individuals which kept their position un- 
changed long enough for the eggs to hatch.” ? 
Professor Whitman proceeds to study the ‘ Disposition 
to Resist Enemies’ and the ‘ Periodicity’ in the same genetic 
way. 
The most important of all original abilities is the ability 
to learn. It, like other capacities, has evolved. The 
animal series shows a development from animals whose 
connection-system suffers little or no permanent modifica- 
tion by experience to animals whose connections are in 
large measure created by use and disuse, satisfaction and 
discomfort. 
Some of this development can be explained without re- 
course to differences in mere power to learn, by the fact 
that the latter animals are given greater stimuli to or re- 
wards for learning. But part of it is due to differences in 
sheer ability to learn, that is, in the power of equally 
satisfying conditions to strengthen or of equally annoying 
conditions to weaken bonds in the animals’ connection- 
systems. This may be seen from the following simple and 
partial case: — 
Call 1 and 2 two animals. 
Call C, and C, the internal conditions of the two animals 
Biological Lectures from the Marine Biological Laboratory of Woods 
Holl, 1898, p. 323 ff. 
