322 



HABIT AND INTELLIGENCE. 



[chap. 



Striated 



muscular 



fibre iu 



Aunulosa 



and in 



Verte- 



brata. 



character of having a skull formed of cartilaginous plates, 

 to protect the cephalic ganglia ; and yet there is no true 

 affinity between the Cephalopoda and the Vertebrata, 

 by the test either of morphological anatomy, or of deve- 

 lopment, or of a gradation of intermediate forms : so that 

 the skulls of the two groups, like their eyes, must have 

 been formed separately. Exactly the same remarks will 

 apply to the fact, that both the Vertebrata and the higher 

 Annulosa have their voluntary muscles formed of striated 

 fibre, while the involuntary muscles of those groups, and 

 all the muscles of the Mollusca, are non-striated.^ If the 

 Vertebrata and the Annulosa have been descended from a 

 common ancestor, that ancestor must have been far too low 

 in the scale to possess striated muscle ; and consequently 

 that tissue must have been formed in those two groups in- 

 dependently. The origin of tissue, however, is so totally 

 unknown, that no argument drawn from it can be of much 

 weight. I have already admitted that I do not see any 

 absurdity in the idea of the muscular, and perhaps even 

 the nervous tissues being, in some way, originally produced 

 by a process of self-adaptation. 



Sponta- 

 neous 

 variation 

 and 

 natural 

 selpction 

 is a pro- 

 cess of 

 blind trial, 



and in- 

 applicable 

 to complex 

 conditions. 



Natural selection among spontaneous variations may be 

 described, without a metaphor, as a process of experiment 

 by mere hlincl trial, and preserving the results of the suc- 

 cessful experiments, while the failures are destroyed and 

 forgotten. I do not deny that great results have been ob- 

 tained in this way. Such has been the case in some 

 chemical arts ; above all, I believe, in photography ; and it 

 is by such a process of blind experimenting, without any 

 acoustic theory to guide the experiments, that musical in- 

 struments have attained to their present high degree of 

 perfection. But this method is applicable only to cases 

 where the process of experimenting is comparatively 

 simple. Were it necessary for ten different experiments at 

 once to be successful, in order that any result at all might 

 be obtained, such a method would be totally inapplicable ; 

 the improbability of success would be an improbability of 



1 Carpenter's Comparative Physiology, p. 442. 



