1898] MR HERBERT SPENCER'S BIOLOGY 383 



peripheral nerve-endings. There is no spot on the skin that is not 

 sensitive to the touch of a pencil-point. And we do not yet know 

 the limits within which education and practice may refine the appli- 

 cation of central powers of discrimination within little-used areas. 

 The facts which Mr Spencer adduces may be in large degree due to 

 individual experience ; discrimination being continually exercised in 

 the tongue and finger-tips, but seldom on the back or breast. We 

 need a broader basis of assured fact. 



It may here be parenthetically noted that Mr Spencer's conten- 

 tion that the nervous system is the result of direct equilibration is 

 difficult to square with the embryological discovery that the axis- 

 cylinders of the afferent spinal nerves take their origin in the nerve- 

 crest (which differentiates into the ganglia on the dorsal roots) and 

 grow outwards to their distribution in the skin or elsewhere. 



A third line of evidence on which Mr Spencer relies is that 

 supplied by vestigial organs, which, he contends, must be due to 

 dwindling through disuse. But the explanation is beset with diffi- 

 culties. Is there any evidence that a structure really dwindles 

 through disuse in the course of individual life ? Let us be sure of 

 this before we accept the argument that vestigial organs afford 

 evidence that this supposed dwindling is inherited. The assertion 

 may be hazarded that, in the individual life, what the evidence shows 

 is that, without due use, an organ does not reach its full functional 

 or structural development. If this be so, the question follows : How 

 is the mere absence of full development in the individual converted 

 through heredity into a positive dwindling of the organ in question ? 

 In our present state of ignorance we can only adopt the form used 

 by Mr Spencer and say : No reply. 



It will be understood that the foregoing considerations are urged, 

 not in support of one hypothesis or in opposition to another, but in 

 advocacy of suspended judgment, of calm and impartial weighing of 

 evidence, and, above all, of further observation and experiment. 

 While the forces of battle are arrayed under the banners All-Suffi- 

 ciency of Natural Selection and Inheritance of Acquired Modifica- 

 tions, there are non-militant biological agriculturalists who till the 

 fields of observation and assert that they in truth provide the sinews 

 of war. It is to them that we must look for conclusive evidence 

 one way or the other. 



We cannot part with Mr Spencer (only for a time it is hoped) 

 without again expressing sincere admiration for his genius and 

 gratitude for his self-sacrificing labours. C. Lloyd Morgan. 



University College, Bristol. 



