THE INFLUENCES OF NURTURE 87 



to its nurture, provided always that there be a modicum 

 of air, moisture, food, warmth, and the other indispens- 

 ables. It is a striking fact that the ovum of a rabbit 

 can develop for two days outside of the body altogether, 

 and the experimental embryologists have shown us that 

 many developing germs can readjust themselves and 

 develop normally after strange disarranging tricks have 

 been played with them. There are some delicate crea- 

 tures, such as the larvae of sea-urchins, which are difficult 

 to rear till one knows the secret, which are readily 

 injured by even slight nurtural changes ; on the other 

 hand, many other developing creatures can within limits 

 adjust themselves to, and develop normally in quite 

 peculiar conditions of life. 



If we take a broad view of development and think 

 of full-fledged behaviour, the same is true. If the new- 

 laid eggs of, say, the Blackheaded Gull be taken from 

 the nest and kept in an incubator in the laboratory 

 until they hatch, and if the young birds be reared in 

 confinement, we get, as every one knows, normal, well- 

 endowed creatures, which will migrate months after- 

 wards when their kinsfolk flying overhead pull the trigger 

 of an inborn predisposition. The whole nurture of these 

 young birds was peculiar, but it did not seem to make 

 much difference. There is evidence, we believe, that 

 some birds which have not known freedom are somewhat 

 handicapped when liberated, not knowing their way 

 about. But the clear fact seems to be that for many 

 creatures changes of nurture need not be of great import" 

 ance as long as the essential conditions of development 



