230 THE PRINCIPLES OF HEREDITY 



is observable, however, among yet lower animals, for example, 

 insects, even if destroyed in large numbers. As the destruc- 

 tion is not selective a new instinct is not evolved, and such 

 animals are incapable of acquiring and communicating alarm. 

 Since the advent of sheep the Kea parrots, and in some 

 districts the descendants of the tame pigs of New Zealand, 

 have become predatory. The American bison and the wild 

 Lapland reindeer when much persecuted abandoned the 

 open plain for the forest. Sparrows in New Zealand have 

 taken to burrowing in cliffs like sand-martins, whereas the 

 cliff-swallow of the Eastern States of America has abandoned 

 the cliffs and now resorts to the eaves of houses. Beavers in 

 Europe no longer build huts and dams. Gulls, which are 

 among the wildest of wild birds on the sea-coast, where they 

 are persecuted, are almost as tame as domestic fowls at 

 London Bridge, where they are fed. Innumerable similar 

 examples might be instanced. All the higher animals may 

 be observed imparting traditional knowledge to their off- 

 spring ; thus predatory animals, every species in its own way, 

 teach their young to hunt. 



390. In order to obtain a clear conception of the distinction 

 between instinct and what we have termed reason, it is 

 useful to contrast the development of an animal whose mind 

 is almost purely instinctive with the development of one 

 whose mind is largely rational. Occasionally the newspaper 

 press makes an announcement which is generally received 

 with perhaps undeserved incredulity. It is stated that, 

 on a lump of chalk or coal being struck and shattered, there 

 has leaped from amongst the fragments a frog, perfectly 

 developed and in full possession of its faculties. It is 

 popularly assumed that the frog is coeval with the chalk or 

 coal. The assumption is, of course, nonsense. No frog ever 

 lived for millions of years. Moreover the frog is an air- 

 breathing animal. On the other hand it is just possible that 

 on very rare occasions a frog may inhabit such a prison- 

 house. If the lump had a cavity in the heart of it, and if, 

 after removal of the lump from, or disturbance in its place of 

 formation, water laden with nutriment flowed into the cavity 

 by one crevice and out by another, a tadpole might make its 

 dwelling in the cavity, till too big to leave it ; and if there 

 were air in the cavity as well as water the tadpole might 

 develop into a perfect frog. It is difficult to decide what 

 amount of truth there is in these newspaper announcements. 

 Probably, since they are so frequently repeated and with so 

 much circumstantial detail, they are not wholly false. The 



