Chap. VI.] AFFINITIES AND GENEALOGY. 179 



independently of the uses to which the several parts may- 

 be put. He passes through the same phases of embryo- 

 logical development. He retains many rudimentary and 

 useless structures, which no doubt were once serviceable. 

 Characters occasionally make their reappearance in him, 

 which we have every reason to believe were possessed by 

 his early progenitors. If the origin of man had been 

 wholly different from that of all other animals, these va- 

 rious appearances would be mere empty deceptions ; but 

 such an admission is incredible. These appeai*ances, on 

 the other hand, are intelligible, at least to a large extent, 

 if man is the co-descendant with other mammals of some 

 unknown and lower form. 



Some naturalists, from being deeply impressed with 

 the mental and spiritual powers of man, have divided the 

 whole organic world into three kingdoms, the Human, the 

 Animal, and the Vegetable, thus giving to man a separate 

 kingdom.* Spiritual powers cannot be compared or classed 

 by the naturalist ; but he may endeavor to show, as I have 

 done, that the mental faculties of man and the lower ani- 

 mals do not differ in kind, although immensely in degree. 

 A difference in degree, however great, does not justify us 

 in placing- man in a distinct kingdom, as will perhaps be 

 best illustrated by comparing the mental powers of two 

 insects, namely, a coccus or scale-insect and an ant, which 

 vmdoubtedly belong to the same class. The difference is 

 here greater, though of a somewhat different kind, than 

 that between man and the highest mammal. The female 

 coccus, while young, attaches itself by its proboscis to a 

 plant ; sucks the sap, but never moves again ; is fertilized 

 and lays eggs ; and this is its whole history. On the 

 other hand, to describe the habits and mental powers of a 



' Isidore Geoffrey St.-Hilaire gives a detailed account of the position 

 assigned to man by various naturalists in their classifications : ' Hist. 

 Nat. Gen.' torn. ii. 1859, pp. lYO-189. 



