276 Animal Intelligence 
“6b. The Incubation Instinct 
1. Meaning to be Sought in Phyletic Roots. —It seems 
quite natural to think of incubation merely as a means of 
providing the heat needed for the development of the egg, 
and to assume that the need was felt before the means 
was found to meet it. Birds and eggs are thus presupposed, 
and as the birds could not have foreseen the need, they 
could not have hit upon the means except by accident. 
Then, what an infinite amount of chancing must have 
followed before the first ‘cuddling’ became a habit, and 
the habit a perfect instinct! We are driven to such pre-- 
posterous extremities as the result of taking a purely casual 
feature to start with. Incubation supplies the needed heat, 
but that is an incidental utility that has nothing to do with 
the nature and origin of the instinct. It enables us to see 
how natural selection has added some minor adjustments, 
but explains nothing more. For the real meaning of the 
instinct we must look to its phyletic roots. 
If we go back to animals standing near the remote an- 
cestors of birds, to the amphibia and fishes, we find the same 
instinct stripped of its later disguises. Here one or both 
parents simply remain over or near the eggs and keep a 
watchful guard against enemies. Sometimes the move- 
ments of the parent serve to keep the eggs supplied with 
fresh water, but aération is not the purpose for which the 
a exists. 
, 2. Means Rest and Incidental Protection to Offspring. — 
| i The instinct is a part of the reproductive cycle of activities, 
and always holds the same relation in all forms that exhibit 
it, whether high or low. | It follows the production of eggs, 
or young, and means “primarily, as I believe, rest, with 
