CAUSES OF STRUCTURAL CHANGES. 699 



the eating of horse-flesh was a part of the ceremonies in 

 the worship of Odin, was the cause of its being prohibited 

 by ancient Cathohc priests and their followers. "St. 

 Olaf, the cruel king who converted the Scandinavians to 

 Christianity by the sword, put to death or mutilated all 

 who persisted in using that heathenish food" (Rollo 

 Springfield). 



Men of the Reindeer Age had evidently some knowledge 

 of drawing and sculpture, because they left behind them 

 many representations of equine animals, most of which are 

 depicted with upright manes, scanty tails, and no fore- 

 locks ; and a few, with stripes. With respect to the 

 manes, tails and absence of forelocks, some of the 

 animals in question would readily pass for Prjcvalsky's 

 horses (p. 640). With regard to the stripes, we have 

 the important fact that horses of the present day often 

 have stripes (p. 330), and the stripes as a rule are more 

 distinct at birth, than when grown up. 



Causes of Structural Changes. — Variation plays 

 a large part in every species of animals, and the 

 members that succeed best in the struggle for existence, 

 are those whose physical and mental powers are most 

 suitable to their surroundings. Hence, evolution is the 

 result of favourable variation being transmitted by here- 

 dity. We have seen in this chapter that the change in 

 the teeth of the horse family has been caused by the 

 forage (and its producer, the soil) becoming gradually drier 

 and harder. The fact that the feet of the tapir have 

 undergone, practically, no modification for millions of 

 years, proves that his present conditions of life are nearly 

 the same as they were when the ancestors of the horse, 

 like those of the tapir, had 4 digits on each fore foot, and 

 3 on each hind one. Feet like these, which, under the 

 influence of pressure, had the faculty of spreading out, 

 were admirably suited for going through soft ground 

 similar to that over which the tapir still roams in a wild 



