334 BIOLOGICAL LECTURES. 



degrees of flexibility, and there is a correspondingly greater 

 freedom of action, with, of course, greater liability to irregu- 

 larities and so-called "faults." These faults of instinct, so far 

 from indicating psychical retrogression, are, I believe, the first 

 signs of greater plasticity in the congenital coordinations and, 

 consequently, of greater facility in forming those new combina- 

 tions implied in choice of action. 



If we place the three grades of pigeons under the same con- 

 ditions and test each in turn in precisely the same way, we can 

 best see how domestication lets down the bars to choice and 

 at the same time gives more opportunities for free action. 

 The simplest experiment is always the best. Let us take 

 three species at the time of incubation and repeat with each 

 the experiment of removing the eggs to a distance of two 

 inches outside the edge of the nest. The three grades are 

 well represented in the wild passenger pigeon {Ectopistes), 

 the little ring-neck {Tiirt7tr risoriiis), and the common dove- 

 cot pigeon {Cohimba livia domestica). The results will not, of 

 course, always be the same, but the average will be about as 

 follows : 



1 . The Passenger Pigeon. — The passenger pigeon leaves 

 the nest when approached, but returns soon after you leave. 

 On returning she looks at the nest, steps into it, and sits 

 down as if nothing had happened. She soon finds out, not 

 by sight, but by feeling, that something is missing. Her 

 instinct is keenly attuned and she acts quite promptly, leaving 

 the nest after a few minutes without heeding the tgg. The 

 conduct varies relatively little in different individuals. 



2. The Ring-neck Pigeon. — The ring-neck is tame and sits 

 on while you remove the eggs. After a few moments she 

 moves a little and perhaps puts her head down, as if to feel 

 the missing eggs with her beak. Then she may glance at the 

 eggs and appear as if half consciously recognizing them, but 

 make no move to replace them, and after ten to twenty 

 minutes or more leave the nest with a contented air, as if 

 her duty were done ; or, she may stretch her neck toward the 

 eggs and try to roll one back into the nest. If she succeeds 

 in recovering one, she is satisfied and again sinks into her 



