118 THE AMERICAN NATURALIST [Vol. LVI 



parallelisms in variation which appear in different 

 branches of the same large group of organisms; (2) those 

 argued from the premise that the very nature of the 

 chemical complexes which constitute the body of a living 

 organism necessarily limit changes to relatively few di- 

 rections; and (3) some of those instanced in the field of 

 palfpontology. 



As to examples of parallelisms in related forms, I am 

 most familiar with conditions to be seen in the color 

 pattt'i'ii- of the ])lioasants {Phasianince) and the guineas 

 (XiniiijUiut ). Ill a ])aper^ written some years ago I sum- 

 marized my observation on various features of the colora- 

 tion in a number of groups of genera and species in these 

 two subfamilies as follows : 



. . . there are certain basic tendencies for particular elements of 

 the coloration, such as the formation of eye-spots, barring, and the 

 like, to follow along definite paths of development. When arranged 

 with reference to one of these elements, such, for example, as bar- 

 ring, which is one of the most universal, instead of possessing dis- 

 tinct and unrelated markings, the different species in a given group 



ment of one, or at most a few, continuous progressions of the special 

 pattern in question. Since when so groui>ed the gradation in 

 pattern is as nnich in evidence between collateral kinsmen as be- 

 tuc( II thos. uf (linci lineage, one can only conclude that the bias 

 fuward a piirficiilai' lint- of patterns is the product of fundamental 

 jirct.ii !a-tiil<- icriil:ai iti( s implanted in the group as a whole. 



Further on in the same ])ai)er it is shown that where 

 the pattern ]ia> hecoitu' obscured it tiiay be brought to ex- 

 pression again through hyl)ri(lizatioii. In tlie interesting 

 group known as tlie i)eaco<-k phen-nnts {Vohjplect'ron) 

 which by sj'stematists is leunrde l as intermediate be- 

 tween the peafowls and the i)he;i-ant> in the narrower 

 sense, the varying stages and type- of ocellation to be 

 seen afford a good illustration of the point at issue. Quo- 

 ting again from this earlier study: 



Again as regards ocelli or " eye-spots " in P. chalcurus, which 

 appears to be the most generalized si^ecies, one finds no ocellation. 

 The only hint of what is to be realized in the more specialized 



1 Jmir. Exp. Zool, VII, 4, 1909. 



