578 Studies in the Theory of Descent. 



11 cover the whole surface of the palatal plates in 

 brush-like tufts." 



How is it possible to regard such widely diver- 

 gent anatomical characters as changes suddenly 

 produced by the action (but once exerted) of de- 

 viating conditions of life ? Hand in hand with the 

 shedding of the old and the appearance of new 

 palatine teeth, there occurs a change in the anato- 

 mical structure of the vertebral column, and also 

 as we may fairly conclude from Kolliker's 

 correct observation of the cessation of the slimy 

 secretion in the histological structure of the skin. 

 Who would undertake to explain all these pro- 

 found modifications as the direct and sudden 

 action of certain external influences ? And if any 

 one were inclined to explain such changes as a 

 consequence of the disappearance of the gills, i.e. 

 as correlative changes, what else is such a corre- 

 lation than the phyletic vital force under another 

 name? 



If from one change arising from the direct 

 action of external agencies, the whole body can in 

 two days become transformed in all its parts, in 

 the precise manner which appears best adapted for 

 the new conditions of life under which it is hence- 

 forward to exist, then the word " correlation " is 

 only a phrase which explains nothing, but which 

 prevents any attempt at a better explanation, and 

 it would be preferable to profess simply the belief 

 in a phyietic vital force. 



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