186 THE DESCENT OF MAN. Part I. 



passes through the same phases of ernbryological de- 

 velopment. He retains many rudimentary and useless 

 structures, which no doubt were once serviceable. Cha- 

 racters occasionally make their re-appearance 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 

 various appearances would be mere empty deceptions ; 

 but such an admission is incredible. These appearances, 

 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. 1 Spiritual powers cannot be com- 

 pared or classed by the naturalist ; but he may endea- 

 vour to shew, as I have done, that the mental faculties 

 of man and the lower animals 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 undoubt- 

 edly 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, whilst young, attaches itself by its pro- 

 boscis to a plant ; sucks the sap but never moves again ; 

 is fertilised and lays eggs ; and this is its whole history. 

 On the other hand, to describe the habits and mental 



1 Isidore Geoffroy St.-Hilaire gives a detailed account of the position 

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

 Nat. Gen.' torn. ii. 1859, p. 170-189. 



