854 



SCIENCE 



[N. S. Vol. XXXVI. No. 938 



and dominates inferior organizations. Be- 

 yond denial there is a specific something, 

 if it be nothing more than accidental chem- 

 ical peculiarities of cells or smaller units, 

 which corresponds to the organization of 

 the individual as a whole. "When, there- 

 fore, we see two organs arising in an em- 

 bryonic cell layer which is otherwise lack- 

 ing in visible differentiation, the distance 

 between these two organs bearing to other 

 dimensions in the embryo a ratio which is 

 fairly constant for embryos of that species, 

 we have before us an instance of the 

 operation of the organization as a whole. 



Many developmental events we may even 

 now attribute, with a fair degree of confi- 

 dence, to organizations of certain grade. 

 Perhaps this is to a greater extent true of 

 the later and more complex developmental 

 operations than of the earlier and simpler. 

 When we see a limited region of a tissue 

 whose physical (in distinction to physiolog- 

 ical) environment can not be far from 

 homogeneous give rise to a structure of 

 considerable complexity, it is highly prob- 

 able that the action of an organization 

 higher than that of the tissue is involved. 

 But who can say whether the typical pro- 

 cess of gastrulation is a function of cells or 

 of cell layers? Do the factors concerned 

 in gastrulation consist of a certain physical 

 environment plus cell organization, or does 

 this process depend essentially upon that 

 higher organization in virtue of which the 

 embryonic cells are associated together in a 

 blastoderm, or does it involve specific fac- 

 tors higher in grade than those which de- 

 termine organization as a mere cell layer? 

 Or, indeed, does it involve no protoplasmic 

 mechanism of any grade, being entirely 

 dependent upon the physical environment 

 and the gross physical properties of the 

 blastula wall? While I am strongly of the 

 opinion that gastrulation depends upon 

 physiological factors of an order higher 



than cell organization, I can not offer abso- 

 lute proof of it. 



When we have identified the grade of 

 the organization responsible for a particu- 

 lar developmental event, our next task-^- 

 doubtless a much more difficult one — will 

 be to discover the location of the dynamic 

 factors which determine that event. Are 

 they numerous, mutually independent, col- 

 lectively uncontrolled, seated in the several 

 elements of the responsible system, the 

 event in question being merely the result- 

 ant effect of their separate operation ? Or 

 does some larger dynamic agent dominate 

 the behavior of all the subordinate mem- 

 bers of the system? When we have ac- 

 complished all this we may well feel en- 

 couraged to press on to the discovery of 

 the mode of operation and the nature of 

 these organic energies. 



THE BEALITT OF ORGANIZATION 



Now the question arises whether this con- 

 ception of organizations of various grades 

 consists in anything more than an artificial 

 and arbitrary classification of the complex 

 phenomena of ontogeny and of the com- 

 plexities of adult structure. Is it not of 

 the same nature and value as our classifi- 

 cation of animals? We have devised a 

 scheme whereby we regard animals as 

 segregated into a series of groups — species, 

 genera and so on — subordinated one to 

 another. We arbitrarily separate these 

 groups by sharp lines. While the scheme 

 expresses, to some extent, our ideas con- 

 cerning the past history of animals, the 

 groups themselves have no real existence 

 "in nature," as we say. There these sharp 

 lines do not exist. The species or other 

 group has no definite limits in space, no 

 form, no integrity. It has no organization 

 as a whole. It is true that some close anal- 

 ogies may be drawn between phylogenetic 



