SUMMARY. 307 



discoveries, and have adopted similar manners and 

 customs and similar religious observances. This 

 allows us to infer that there is a physical and 

 psychical unity of human nature which indeed 

 separates into races and varieties, but not into 

 distinct species. Certain tokens of what is hypo- 

 thetically the primeval type will predominate even 

 in the progeny which has been modified by a distinct 

 and separate development, and we need not be 

 surprised by reversions to the animal structure, 

 even in man, the ultimate scope of organic develop- 

 ment. Nor will the developed culture of man offer 

 any hindrance to such reversions. The theromorphic 

 conditions which we have pointed out in the third 

 chapter of this work, such as the frontal process of 

 the squamous temporal portion, the transverse 

 enlargement of the occipital bone, the pointed 

 ear, etc., occur both in the higher and lower races 

 of man ; just as, for example, both in primitive and 

 high-bred races of horses there are reversions to 

 fossil forms in hind toes, cloven hoofs, etc. 



Not only the physical, but the mental develop- 

 ment of man advances uniformly, and not per saltum. 

 Physical qualities and defects may occur in a given 

 number of negroes and Papuans, and may be absent 

 in an equal number of Europeans, and conversely 

 may occur in the one and be absent in the other ; 

 yet, in their mental condition, negroes and Papuans 

 must always be regarded as in a lower order than 

 Europeans. And if physical superiority is more 

 widely diffused in European peoples than elsewhere, 

 owing to higher culture, less exposure, and better 



