LECT. ii BASIS OF EXPERIMENTAL EVOLUTION 47 



to be briefly stated in order to show how experimental 

 transformism must be carried out. Of course it is of 

 much importance to prove that living organisms 

 display a marked tendency to vary, under natural con- 

 ditions, in most of their parts, in a more or less marked 

 degree. For this natural variability l is that which 



1 Cornevin (Traitc de Zootechnie generate, 1891, p. 226) establishes 

 the following list of the modes of variation among domestic animals : 



I. Morphological variations. 



Variations through disappearance. Absence of horns, ears, 



hair, pigment, etc. 

 Total. Dwarfing, discolour- 

 ation. 



arrested ' Partial. Niatism, partial 



development, j discolouration, reduction 

 in the number of limbs, 

 etc. 



juxtaposition. Is seen in some hybrids 

 when the characters of 

 both progenitors coexist 

 side by side. 



fusion. Diminished number of 



ribs, teeth, digits, verte- 

 brae, etc. 



transformation. Wool replaced -by hair; 



scales replaced by fea- 

 thers, etc. 



j Total. Giants, melanism, 

 ; extreme hairiness. 



- hypertrophy. Partial Drooping ears ; 

 very long horns, hairs 

 or feathers of unusual 

 length. 



( Supplementary vertebrae 

 division or ribs, teeth, horns, digits, 



repetition. / 



