ment in favour of design; for either the cold and snow-glare fail in their normal effect in the case of animals that do not require the protection of white colour, or the fur of such animals was in some way modified so as not to be susceptible to the influence that cold and snow-glare are alleged to have.

It may be presumed that the colour of animals was adjusted to maintain the balance of life among different races. The colour of some animals aids them to capture their food, and of others to escape from becoming food. Again, in some cases colour may be a danger-signal to possible victims, and in others add to the perils of its possessor, who, it may be assumed, has a compensating advantage in some other direction.

may

How can common-sense accept this marvellously delicate and intricate adjustment of the balance of life, partly by colouring and partly by faculties, as the self-evolved outcome of conflicting forces, or of what is called Chance?

The Shetland Pony.

The diminutive size of the Shetland pony has been attributed to adverse conditions of

existence for many generations, but recent experience in breeding the pony in England negatives this assumption.

A stud of Shetland ponies was established in 1882 at Holinside Old Hall Farm, near Chester-le-Street, and its manager, writing in 1898, reports that the " tendency [in height] is downwards, in fact of recent years decidedly downwards," and the herd-book of the breed confirms this statement.

The experience in breeding the pony under changed and more favourable conditions throws some light on the limits of development, and approximately on the amount of oscillation round the average type.

Before the pony attracted attention by its diminutive size, the Shetland farmers bred with an eye to increase the height, to make the animal more serviceable as a beast of burden; but when the pony came to be used in the Durham collieries, the breeders sought to diminish the height and selected the smallest sires. By this selective breeding the average height of the pony, as the herd-book shows, has been reduced about three inches say seven per cent. The decrease in height must be due solely to selection, for better food and greater comfort in their southern quarters than in their

Shetland homes should have tended to increase their size.

There is no history or tradition of the origin of the Shetland pony. So far as known, it has always been an inhabitant of the Shetland Islands, and its characteristics have never changed. The ponies are remarkable for good temper, freedom from vice, and docility even when not handled for years, and their intelligence contrasts very favourably with that of Iceland ponies, and indeed with that of any other breed of horses. Their mature crop of hair does not come until they are three or four years old, their previous coat being more like wool than hair. These characteristics both in physique and character, coupled with the breeding experience, justify, in the absence of evidence to the contrary, the conclusion that the Shetland pony is a distinct race, and that its small size was not brought about by unfavourable external conditions of life.

Physiological.

The genesis of an organism clearly indicates that external influences cannot produce specific variation.

The embryo is the product of special forces

in the germ-cell, and the embryo develops into a foetus that in due time evolves an adult of the type that produced the germ-cell. This outcome, except for accident, is invariable, and we conclude that before there can be any specific variation in a type there must be some change within the germ-cell of that type. But how can external influences affect the germ-plasm? A seed may, as we have seen, be stunted by climatic or other unfavourable influences; but if it do grow, it invariably produces an organism of its parental type.

CHAPTER XII.

INSTINCT AND HABIT.

DARWIN deals with the development of instinct on the same lines as the evolution of life. He assumes the existence of instinct in a simple form, and holds that complex instincts are the results of the accumulation of numerous successive slight modifications of simpler instincts. He, however, admits that certain instincts of bees and ants could not have been acquired. These have come by

spontaneous variation": others are the result of acquired habits inherited through many generations; these he calls "domestic habits." But beyond general statements Darwin gives no example of the appearance of a new instinct, or of an acquired habit becoming hereditary.

There is no evidence of any variation in the nature of an instinct, although, like other characteristics, it varies in degree in different members of the same race, and may to some