ON HEEEDITY. . 95 



A number of species exists at the present day, of which the cocoons 

 can be arranged in a complete series, becoming gradually less and 

 less complex, from that described above, down to a loosely-con- 

 structed, 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 con- 

 structed without assistance from the experience of the single 

 individual and this must certainty 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 cannot 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 dis- 

 positions, but combinations of many dispositions, and often of 

 a most complex nature : they depend upon a certain degree of 

 irritability, and a power of readily transmitting impulses along the 

 nerve-tracts of the brain, as well as upon the especial development 

 of single parts of the brain. In my opinion, there is absolutely no 

 trustworthy proof that talents have been improved by their exercise 



