814 



SCIENCE 



[N. S. Vol. XXXVI. No. 937 



sponding to organs, tissues and cells. But 

 the agent which dominates these lower or- 

 ganizations and produces the organization 

 into a whole individual has somehow disap- 

 peared. 



The first view we may conveniently des- 

 ignate as the theory of autonomous ele- 

 ments, understanding that this autonomy 

 does not preclude the possibility that the 

 environment in which each element lives 

 may depend in a great variety of ways upon 

 the operation of other systems. The sec- 

 ond view we may call the theory of con- 

 trolled elements or the theory of domi- 

 nance, referring to the existence of specific 

 agents which dominate and coordinate the 

 form and behavior of structural elements. 



The problem of organization in the form 

 in which I have here stated it has no defi- 

 nite relation to that problem of ontogeny 

 whose alternative and opposed answers 

 have from time to time and with ever 

 shifting significances borne the names pre- 

 formation (or evolution) and epigenesis. 

 The theory of autonomous elements associ- 

 ates itself very consistently with the idea 

 of a considerable degree of rigid germinal 

 preformation — mosaic development. Never- 

 theless, a scheme of development whicli is 

 to the fullest possible extent epigenetic 

 may be thought of as depending essentially 

 upon the ever-changing environment of 

 each individual element, the orderly series 

 of successively determined stages proceed- 

 ing in the total absence of specific form-de- 

 termining agents exercising immediate con- 

 trol over groups of elements. The theory 

 of dominance may likewise be consistently 

 linked with either conception of the mode 

 of development. Let it be assumed that 

 the harmonious operation of any onto- 

 genetic system, such as the concerted action 

 of the entoderm cells in gastrulation, be 

 due to the presence of an agent which 

 coerces the elements of the system into 



that particular form of behavior, even in 

 spite of some differences which may exist 

 amongst those elements and in spite of 

 some degree of inequality in their several 

 environments — ^an agent in whose absence 

 there would be no concerted action at all. 

 We then have our choice of these two alter- 

 natives. We may attribute the existence 

 and timely operation of the control agent 

 directly to some peculiarity of the germ — 

 preformation; or we may suppose it to 

 arise as a function of the preceding stages 

 in development, being thus only indirectly 

 related to the original germ organization — 

 the epigenetic view. 



Neither does the line between our two 

 conceptions of the nature of organization 

 coincide with the line separating those two 

 groups of theories known as mechanistic 

 and vitalistie. This statement can the more 

 confidently be made in view of the fact that 

 there is serious disagreement as to where 

 the latter line really lies. The theory of 

 autonomous elements leads almost neces- 

 sarily to a mechanistic view of the organ- 

 ism. Factors which are in any sense to be 

 regarded as vitalistie could scarcely be 

 introduced save by actual violence. The 

 theory of dominance, however, affords 

 ample latitude for the extremes of these 

 two groups of opposed philosophical atti- 

 tudes. If it is possible to imagine that the 

 harmonious action of a system is the re- 

 sultant effect of the coincident operation 

 of the mechanisms of its autonomous ele- 

 ments, it is equally possible to imagine that 

 mechanisms have arisen on a larger scale, 

 not confined within the limits of a single 

 element, but embracing groups of elements. 

 To think of such a larger mechanism 

 operating through or by means of the ele- 

 ments embraced within its scope, or 

 operating within the substance of a group 

 of elements irrespective of its subdivision 

 into elements, gives us the picture of a 



