856 



SCIENCE 



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



no evidence that a species or other group 

 contains any organization higher than that 

 of its members as individuals. This lack 

 of form in the phylogenetic group is most 

 significant in the present connection, for 

 it affords us an example of what results, 

 in the ivay of form, from the action of 

 physical environment on a group of living 

 units possessing no organization higher 

 than that of each individual as such. In 

 contrast to this we see everywhere in on- 

 togeny precisely coordinated action of nu- 

 merous elements resulting in forms which 

 are not only definite, but elaborate. The 

 physical environment in ontogeny may be 

 considerably altered, yet these forms insist 

 upon developing. Is it not futile, at this 

 stage of our knowledge, to attempt to think 

 of tissues originating in ontogeny by the 

 action of a physical environment upon in- 

 different cells, or to think of organs arising 

 similarly from indifferent tissues? "While 

 it is becoming that science, as well as scien- 

 tists, should be modest in its claims, never- 

 theless to underestimate our knowledge 

 merely retards progress. We now possess 

 a large body of well-authenticated data 

 upon ontogeny. I can not see in these 

 data the least evidence that an environ- 

 ment which is, in the ordinary sense, 

 purely physical — that is, devoid of specific 

 physiological factors — has any power what- 

 ever to organize living substance. Upon 

 the other hand there is every evidence that 

 organization arises within the living sub- 

 stance and that the living organizes the 

 non-living. To admit that originally the 

 living arises spontaneously from the non- 

 living by any such process as fortuitous 

 concourse of atoms is explicitly to deny 

 that the non-living has organizing power, 

 for then organization begins by accident 

 and higher organizations could arise only 

 by continuance of accidents within the 



living substance itself, environment merely 

 acting selectively. Even if chance is the 

 creative element in phylogeny, it is not so 

 in ontogeny. The development of the in- 

 dividual does not progress by trial and 

 error. 



We must admit, I believe, that in onto- 

 geny cells are somehow directly and actively 

 organized into tissues, and tissues and cells 

 are still further organized into organs. 

 The physical environment of a group of 

 embryonic cells is no more capable of or- 

 ganizing those cells into a higher complex 

 of elaborate form, than is that larger en- 

 vironment in which the whole animal lives 

 capable of directly determining in ontog- 

 eny the form of the animal as a whole. 

 I see no escape from the conclusion that 

 specific organic or physiological factors — 

 djTiamic factors seated in protoplasmic 

 structure — are involved in this organizing 

 of lower structural elements into higher. 



Furthermore, our analysis of the adult 

 organism into organs, tissues and cells of 

 various kinds is not, to any important 

 extent, arbitrary. Here sharply drawn 

 lines do exist. In the adult animal we do 

 not find cells which constitute a continuous 

 graded series between two distinctly differ- 

 ent types of cells. A cell is either one 

 thing or another. Neither do the several 

 types of tissues in any individual merge 

 indistinguishably one into another, as do 

 species. In ontogeny a cell of one type 

 may become transformed into a cell of 

 another type, passing gradually through 

 all the intermediate conditions. But the 

 change is completed so that ultimately the 

 cell is distinctly of one type and not of the 

 other. If in the adult animal there are 

 ' ' indifferent cells, ' ' they are not indifferent 

 in the sense of being indefinitely inter- 

 mediate in character between cells of dif- 

 ferent types. Their very indifference eon- 



