XVI ARE ACQUIRED CHARACTERS INHERITED? 331 



priately varied." The same assumption pervades the 

 writings of most of the opponents of Weismann. Thus 

 Mr. Keeler, in the work already quoted, says, referring to 

 the modification of organs by variation and selection only : 

 " This explanation is open to two objections : first, the one 

 already raised by Mr. Spencer, that before the second 

 correlative variation appeared the first would be lost ; and, 

 second, the suggestion of Cunningham in regard to 

 assuming that use could develop the character required, 

 but that the individual thus favoured could not transmit 

 the variation, but that posterity must wait for the same 

 variation to arise spontaneously. This hypothesis is so 

 forced, illogical, and absurd, that so long as a better one 

 can be found it should be adopted." 



Now all this implies that there are but few variations 

 occurring at long intervals; the facts being that, in 

 populous species, every generation affords many thousands 

 of variations of every observable part and organ ; whence it 

 follows that the individuals of every such species can be 

 divided into two sets as regards each organ or each group 

 of parts, such as those with a longer and those with a 

 shorter neck, those with neck and legs longer and those 

 with the same parts shorter. In the latter case perhaps a 

 quarter or an eighth only of the whole population would 

 be found in each category ; but as, in most cases, not one 

 eighth part of those born each year can survive, this 

 would be ample. It will be seen that the facilities for 

 modification are thus indefinitely greater than the expres- 

 sions and arguments of Mr. Spencer and his supporters 

 assume them to be. 



Another tacit assumption is, that in nature all the 

 individuals of a species have their parts so perfectly co- 

 ordinated that any increase of one part only would disturb 

 the harmonious adjustment and be a disadvantage. But 

 this is totally to misconceive the situation. The adjust- 

 ment of parts is a rough working adjustment, sufficient 

 for the purpose of maintaining life, but capable of being 

 improved (or deteriorated) by very many slight modifica- 

 tions of single parts. To illustrate this general adjust- 

 ment, let us suppose we have before us for comparison all 



