ORGANIC VARIATION AS A CRITERION OF 
DEVELOPMENT. 
THOS. H. MONTGOMERY, Jr., Pu.D. 
CONTENTS. 
PAGE 
EN PRODUCT ORY = hc.cetetccse ssi vse csestedcdes 208s dicispa0- le cca ne asnsttessecnoepnes napeeeceaeenes weno 251 
I. DEFINITION OF VARIATION; CORRELATION OF ORGANS; PROGRES- 
SIVEVAND! (REGRESSIVE, IDEVELOPMENT. ¢...2-..-ccsescesees secuestseeessseeeesee 253 
II. CONTINUING ORGANIC DEVELOPMENT IS ALWAYS ACCOMPANIED BY 
PUPAE ICT gs Red Ue ceo coco oA en sence scence en ea eee 259 
A. Certain Criteria of Continuing Developmtent.........-...cccecce co 259 
TES Wy 22) 2028 Sree eRe ar eee ae Nn cA ons Sd ek Ie ge 264 
C™eDinech Injercucesaprom the: Tabulated: Data ete 290 
TONG THE ORIGING OF IVAARTATION yee pole. a. eee eee 293 
IV. ON VARIATION AS A CRITERION OF DEVELOPMENT........-:::cc:ceeeeeeeesees 298 
INTRODUCTORY. 
THE object of the present paper is, firstly, to give a tentative 
explanation for the origin of variation, deducible from the law 
of the concomitance of variation with continuing development. 
The attempt will then be made to show that variation is caused 
indirectly by change of environment, and directly by the dis- 
turbance of correlation of the organs, resulting from the change 
of environment. And secondly, the attempt will be made to 
determine whether, in a given organism, the amount (or degree) 
of variation, and the manner of its occurrence, can furnish us 
with criteria for judging its lines of development. The only 
postulates necessary for the treatment of the problem of varia- 
tion from this point of view are: (1) the concomitance of 
variation with continuing development, (2) the correlation of the 
organs of an organism, as necessary for its existence, and (3) 
the influence exerted upon the organism by its environment, 
necessitating a degree of adaptation to its environment. 
