39© NATURAL SCIENCE. June, 1895. 



more of these numerous slight variations become extra stimulated by 

 a new environment, then, they may become varietal, provided the 

 stimulus be prolonged sufficiently to " fix " the character. Thus 

 Ranunculus Ficaria has become as stated, the var. Caltlwfolia in Malta, 

 etc. ; while Caltha palustris has become C. minor on mountains, and 

 has (it is believed) developed the variety plena under cultivation. 



One more quotation from the writer in Natural Science : — 

 " Although Professor Weldon did not say so, it must have occurred to 

 many listeners that this first result of statistical inquiry on variation 

 was in direct contradiction to those who assert that variation is not a 

 matter of' chance,' but that it occurs in determined directions (p. 218)." 

 As far as the ordinary, but innumerable, slight variations, due to 

 growth and development, are concerned, they may very well be 

 attributed to chance ; for they are the results of accidental differences 

 of nutrition, light, etc., and are, as Mr. Wallace rightly calls them, 

 " non-specific." But I, for one, do maintain that true varietal and 

 specific variations do occur in determined — but certainly not pre- 

 determined — directions ; because they do not arise until some external 

 and sufficient cause occur to determine the special direction in which 

 any particular organ, or organs, of the organism shall grow and 

 develope — as I have shown in the example of Caltha palustris and C. 

 minor. Ex uno disce omnes. 



George Henslow. 



