200 PROCEEDINGS OF THE ANATOMICAL AND ANTHROPOLOGICAL 



features has apparently become more or less fixed in certain races, of 

 whom we have historical evidence, that they have lived for long 

 periods of time, under, presumably, similar external conditions, such 

 as the ancient and modern Egyptians. I am inclined to think, how- 

 ever, that variations in external conditions, such as climatic changes, 

 and the changes of habit which accompany civilisation, will tend, by 

 favouring certain variations, to bring about comparatively rapid 

 changes in type, but that there will always be a strong tendency 

 towards reversion to the more primitive and more stable parent stock. 



6. VARIATIONS IN THE FORM AND SIZE OF THE HEAD ASSOCIATED 

 WITH VARYING DEGREES OF MENTAL ABILITY AND VARIATIONS 

 IN THE FORM OF THE SKULL DUE TO VARIATIONS IN THE FoKM 

 OF THE BRAIN. 



Now although there are great individual variations in the form 

 and size of the head among individuals of high or low degrees of 

 ability, so that in the vast majority of cases we are not able to judge 

 with certainty, from an examination of the head, whether an indivi- 

 dual is above or below the average of intelligence, there are certain 

 features, such as I have described as being characteristic of the skulls 

 of savages and prehistoric man, which, when associated with small 

 size of the cranial portion of the head, are indicative of a low order of 

 intelligence ; and conversely there are certain features, seen in a well- 

 proportioned head such as that of Frederic Schiller's, which do indicate 

 ability. 



The mental powers of the individual, however, may or may not 

 have been developed, and in some cases may even have deteriorated. 

 Thus though in extreme cases it is possible to judge from external 

 appearances that an individual is an idiot, or of a low order of intelli- 

 gence, it is by no means so easy to be certain that an individual has a 

 high degree of ability. 



If we take the nrcrmje measurements, however, of a large number 

 of individuals belonging to a particular class, it will be found that there 



