78 CAUSES OF VARIATION. [iNTROD. 



be compounded together in the middle line forming a single, 



-\ mnietrical organ. 



I- would probably help the science of Biology if the word 

 1;. . raion' and the- ideas which it denotes, were wholly dropped, 

 uts until Variation has been studied much more fully 

 than it has yet been. 



In the "light of what we now know of the process of repro- 

 duction the phrase is almost meaningless. We suppose that a 



tin stock gives off a number of individuals which vary about 

 a normal; and that after having given them off, it begins to 

 pve ..IV individuals varying about another normal. We want 



saj that among these it now and then gives off one which 

 approaches the first normal, that shooting at the new mark it 

 n..\\ and th.-n hits the old one. But all that we know is that 

 now and then it shoots wide and hits another mark, and we 

 assume from this that it would n<t have hit it if it had not 

 aimed at it in a bvgone age. To apply this to any other matter 

 \\onld be ab-urd. '\\V might as well say that a bubble would 

 1..- r-niiid if the air in it had not learned the trick of round- 

 nesfi bv having been in a bubble before: that if in a bag after 

 pulling '"it a lot of white balls I find a totally red one, this 

 pn. M-.S that the bag must have once been full of red balls, or that 

 tin- \\hite ones must all have been red in the past. 



lie-id.--, tli.- logical absurdity on which this use of the theory 

 ot' Reversion rests, the application of it to the facts of Variation 

 bp-ak- d'.un again and again. I have already mentioned some 

 cases of this, but there are many others of a different class. For 

 in-tan.-.-, it will be shewn that the percentage of extra molars 

 in the Anthropoid A p.-- is almost the highest reached among 

 mammals. On the usual interpretation, such teeth are due to 

 Ke\. -i-sioii to an ancestral condition with 4 molars, and on less 

 evidence it ha- been argued that a form frequently shewing such 

 |;< \ersion " is older than those which do not. From this reason- 

 in:; it ,-hould follow that the Anthropoids are the most primitive 

 form, at lea-t ..f monkeys. It is surely time that these brilliant 

 and facile deduction- were no more made in the name of science. 



.'{. CtlUXi'S of Vi. 



[nquiry into the cau-es ,,f Variation is as yet, in my judgment, 

 premature. 



\. Tin' \'<irinliilifi/ <>f " useless " Structures. 



The often-repeated -latemeiit that " useless " parts are 

 .-pecially \ariable. finds little support in the tacts of Variation, 



pt in a- far a- it i- a misrepresent at ion of another principle. 

 Th. examples taken to support- this statement are commonly 



m- -landing at the end of a Meristic Series of parts, in which 



