i)6 ON HEREDITY. [11. 



but during the development of numerous, consecutive species 

 — by gradual and unceasing improvements in the initial stages 

 of cocoon-building. A number of species exists at the present 

 day, of vi'hich the cocoons can be arranged in a complete series, 

 becoming gradually less and less complex, from that described 

 above, down to a loosely-constructed, spherical case in which 

 the pupa is contained. 



The cocoon spun by the larva of Saturnia carpini differs but 

 little in complexity from the web of the spider, and if the 

 former is constructed without assistance from the experience 

 of the single individual — and this must certainly be admitted — 

 it follows that the latter may be also built without the aid of 

 experience, while there is neither reason nor necessity for 

 appealing to the entirely unproved transmission of acquired 

 skill in order to explain this and a thousand other operations. 



It may be objected that, in man, in addition to the instincts 

 inherent in every individual, special individual predispositions 

 are also found, of such a nature that it is impossible that they 

 can have arisen by individual variations of the germ. On the 

 other hand, these predispositions — which we call talents — can- 

 not have arisen through natural selection, because life is in no 

 way dependent upon their presence, and there seems to be 

 no way of explaining their origin except by an assumption of 

 the summation of the skill attained by exercise in the course 

 of each single life. In this case, therefore, we seem at first 

 sight to be compelled to accept the transmission of acquired 

 characters. 



Now it cannot be denied that all predispositions may be 

 improved by practice during the course of a life-time,— and, in 

 truth, very remarkably improved. If we could explain the 

 existence of great talent, such as, for example, a gift for music, 

 painting, sculpture, or mathematics, as due to the presence or 

 absence of a special organ in the brain, it follows that we could 

 only understand its origin and increase (natural selection being 

 excluded) by accumulation, due to the transmission of the 

 results of practice through a series of generations. But talents 

 are not dependent upon the possession of special organs in the 

 brain. They are not simple mental dispositions, but combina- 

 tions of many dispositions, and often of a most complex nature : 

 they depend upon a certain degree of irritability, and a power 



