178 ORTHOGENETIC EVOLUTION IN PIGEONS. 



The formula, as I have said, makes phylogeny the primary fact and ontogeny 

 merely its hereditary repetition, condensed and modified in adaptation to condi- 

 tions. Phylogeny is thus viewed as the necessary antecedent, and hence as the 

 causal foundation of ontogeny. Phylogeny is viewed as the outcome or product 

 of environmental causes, while ontogeny appears as the hereditary re-rendering 

 of this product in the order of its cumulative acquisition. 



We have then, according to this view, two quite distinct series of events, with 

 causal relations equally distinct. In one case the causes are predominantly internal 

 and limited to specific ends, and their work proceeds with clock-like regularity, 

 ending punctually and within a brief time in the production of the individual. 



In the other case, the causes are predominantly external, multifarious, and direc- 

 tionless, and their work is aimless and tentative ending in this, that, or other unpre- 

 dictable result. Chance and utility are supreme in this field. 



So far I have but sketched the prevailing view, and have barely alluded to what 

 seems to me to be a source of misconception and confusion to the advocates of the 

 law, and at the same time a fair provocation for criticism. We may now look for 

 the essential truth of the biogenetic formula. When we take two aspects of one 

 and the same thing and dwell on their contrasts, the point of departure, where 

 truth lies, may be lost sight of. 



In the case of ontogeny and phylogeny we push the error to the point of self- 

 contradiction, by putting phylogeny before ontogeny. The moment we return to 

 basal facts we discover that apart from ontogeny there is no phylogeny. All that 

 we call phylogeny is to-day, and ever has been, ontogeny itself. Ontogeny is, then, 

 the primary, the secondary, the universal fact. It is ontogeny from which we depart 

 and ontogeny to which we return. Phylogeny is but a name for the lineal sequences 

 of ontogeny, viewed from the historical standpoint. It gives us the lines of conti- 

 nuity in descent and enables us to read illuminating sequences in the origin of 

 species, characters, structures, etc. When we can arrange ontogenetic events in 

 the order of genetic dependence, we are in a position of great advantage in the search 

 for causal relations. But these relations have no physical basis outside of ontogeny, 

 and no outside existence except as mental constructions. 



From this point of view the biogenetic law stands for an indisputable, funda- 

 mental, and universal fact — indeed, the central fact of all organic development. 

 Stated in conformity to facts now known, the formula may be revised as follows: 



Ontogeny is reproductive recapitulation, and germinal variation is the source of all 

 phyletic deviation in ontogeny. 



Thus stated, we remove the source of contention, namely, the assumption that 

 phylogeny shapes itself through the transmission of characters acquired in the 

 Lamarckian sense, and that ontogeny comes in secondarily to retrace the path 

 determined by somatic modifications. The old formula obscures the fundamental 

 fact that recapitulation is simply reproductive repetition, and at the same time 

 misrepresents causal relations. To say that modifications functionally acquired in 

 the soma are reflected back upon the germs of the coming generation in such a 

 precise way as to repeat themselves in ontogeny, independently of original causes, 

 is to turn the original sequence upside down. The form-sequence in ontogeny 

 always runs forward or upward, and the causal sequence must of necessity run in 

 the same direction. The contrary view is a wholesale perversion of the problem 



