372 THE INDUCTIONS OF BIOLOGY. 



and there is proof that in many of the lower animals the 

 period of sexual activity is accompanied by a special bodily 

 state sometimes such that the flesh becomes unwholesome 

 and even poisonous. But a change of this kind can hardly 

 account for a structural change in the vocal organs in Man. 

 No hypothesis of gemmules or determinants or physiological 

 units enables us to understand how removal of the testes 

 prevents those developments of the larynx and vocal cords 

 which take place if they remain. 



The inadequacy of our explanations we at once see in 

 presence of a structure like a peacock's tail-feather. Mr. 

 Darwin's hypothesis is that all parts of every organ are con- 

 tinually giving off gemmules, which are consequently every- 

 where present in their due proportions. But a completed 

 feather is an inanimate product and, once formed, can add to 

 the circulating fluids no gemmules representing all its parts. 

 If we follow Prof. Weismann we are led into an astounding 

 supposition. He admits that every variable part must have 

 a special determinant, and that this results in the assumption 

 of over two hundred thousand for the four wings of a butter- 

 fly. Let us ask what must happen in the case of a peacock's 

 feather. On looking at the eye near its end, we see that the 

 minute processes on the edge of each lateral thread must 

 have been in some way exactly adjusted, in colour and posi- 

 tion, so as to fall into line with the processes on adjacent 

 threads : otherwise the symmetrical arrangement of coloured 

 rings would be impossible. Each of these processes, then, 

 being an independent variable, must have had its particular 

 determinant. Now there are about 300 threads on the shaft 

 of a large feather, and each of them bears on the average 1,600 

 processes, making for the whole feather 480,000 of these pro- 

 cesses. For one feather alone there must have been 480,000 

 determinants, and for the whole tail many millions. And 

 these, along with the determinants for the detailed parts of 

 all the other feathers, and for the variable components of all 

 organs forming the body at large, must have been contained 



