THE EVOLUTION OF MAN 195 



and unnecessarily abundant language. He says that since 

 " Nature " has endowed animals with the power of making not 

 all possible acquirements but only certain fixed acquirements 

 that are commonly useful to the species, therefore species differ 

 not only in characters which are inborn but also in those which 

 are acquired ; for instance, the fore-limbs of both ox and man 

 grow greatly in response to use, but the lines of growth are 

 very different. Exactly. Of course Dr. Reid assumes that the 

 difference in the power of making acquirements is due to natural 

 selection. The power of growth in response to exercise resides^ 

 he says, not especially in the parts which are most used, as 

 joints, teeth, or tongue, but in the parts in which it is most 

 useful ; in other words in those parts where it has been evolved, 

 not by use, but by natural selection. It would be difficult to 

 compress a greater number of fallacies into such few words. 

 The chief fallacy lies in the word use ; use of a muscle means 

 contraction, and contraction causes growth of muscle ; but it is 

 obvious that joints do not contract and that a joint has no size. 

 The fact that joints can be developed by use is proved by their 

 actual formation occasionally in neglected fractures. It is also 

 obvious that the tongue, being a muscular organ, is developed by 

 exercise, not merely in absolute size, but in the complexity and 

 precision of its movements, as in the muscles of the hand ; 

 otherwise we could not learn to speak. In fact, it is precisely 

 because the power of acquiring certain structural adaptations 

 resides in those parts which are used for certain purposes that 

 Lamarckians conclude that the power to acquire and the 

 acquirement are due to the same causes, in other words that 

 the hereditary or congenital factor and the acquired factor in 

 adaptations are both due to external stimuli. The contrary 

 view is mere assertion based on no evidence. What evidence, 

 for instance, is there that the ancestor of man possessed a 

 variation in the power of acquiring the upright position, in- 

 dependently of the attempt to walk on his hind legs ? 



Dr. Reid supposes that this power of making acquirements 

 is greatest among the higher animals, and little or not at all 

 present in the lower animals and plants. He instances the frog, 

 and expresses his belief that a tadpole enclosed in a hole or 

 crevice, if supplied with food, would develop into a perfect frog, 

 and that this is possibly the explanation of those cases reported 

 in the newspapers from time to time of perfect frogs found 



