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390 GENERAL SUMMAEY Part II. 



heart) imperfectly developed. This animal seems to 

 have been more like the larvae of our existing marine 

 Ascidians than any other known form. 



The greatest difficulty which presents itself, wlien 

 we are driven to the above conclusion on the origin of 

 man, is the high standard of intellectual power and of 

 moral disposition which he has attained. But every one 

 who admits the general principle of evolution, must see 

 that the mental powers of the higher animals, which 

 are the same in kind with those of mankind, though 

 so different in degree, are capable of advancement. 

 Thus the interval between the mental powers of one 

 of the higher apes and of a fish, or between those 

 of an ant and scale-insect, is immense. The develop- 

 ment of these powers in animals does not offer any 

 special difficulty ; for wath our domesticated animals, 

 the mental faculties are certainly variable, and the 

 variations are inherited. No one doubts that these 

 faculties are of the utmost importance to animals in a 

 state of nature. Therefore the conditions are favour- 

 able for their development through natural selection. 

 The same conclusion may be extended to man; the 

 intellect must have been all-important to him, even at 

 a very remote period, enabling him to use language, 

 to invent and make weapons, tools, traps, &c. ; by 

 which means, in combination with his social habits, 

 he long ago became the most dominant of all living 

 creatures. 



A great stride in the development of the intellect 

 will have followed, as soon as, through a previous consi- 

 derable advance, the half-art and half-instinct of lan- 

 guage came into use ; for the continued use of language 

 will have reacted on the brain, and produced an in- 

 herited effect ; and this again will have reacted on the 



