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SCIENCE. 



[N. S. Vol. XXIV. No. 610. 



ing the persistent faith of the apostles of me- 

 chanical causation, such as Cope, Hyatt, Dall 

 and Dr. Ortmann himself. In short, it does 

 not appear that the true, efficient causes of 

 evolutionary motion are to be found in the 

 phenomena covered by these four terms, in 

 the senses in which they are employed by Dr. 

 Ortmann. 



The conception of which Dr. Ortmann an- 

 nounced a discussion, but has not really con- 

 sidered, definitely abandons these supposed 

 causes of evolution as inadequate and irrele- 

 vant and would elevate to primary importance 

 two considerations generally ignored entirely, 

 or given very subsidiary attention. These are 



(1) heterism, the normal diversity of the indi- 

 viduals of which species are composed, and 



(2) syrnbasis, the free interweaving of the 

 lines of descent of these normally diverse indi- 

 viduals. 



The progressive transformation of species is 

 made possible by these two factors, and it has 

 not been shown that any of the others are to 

 be reckoned as direct or actuating causes, not- 

 withstanding the vast amount of attention 

 devoted in the last half century to the many 

 static doctrines under which evolution has 

 been ascribed to one or another form of en- 

 vironmental influence. 



It may yet be ascertained, perhaps, that the 

 environment does in some way exert actuating 

 influences upon evolution, but it is not too 

 much to say that up to this time all theories 

 of environmental causation remain purely 

 speculative. Heterism and symbasis, on the 

 other hand, though long neglected as evolu- 

 tionary causes, are thoroughly established 

 facts of obvious implication. Individual di- 

 versity persists in spite of uniformity of con- 

 ditions, and interbreeding is everywhere co- 

 incident with evolutionary progress. Even on 

 purely mathematical grounds it becomes ap- 

 parent that the resultant of the continuous 

 interweaving of diverse lines of descent must 

 be a progressive transformation of type. 



Dr. Ortmann points out that de Vries has 

 confused speciation with variation, but might 

 be charged in turn with having confused evo- 

 lution with variation, just as so many other 



writers have confused evolution with specia- 

 tion. Why so many attempts at leaving 

 Hamlet out of the play ? Each is a testimony 

 of the surviving strength of the old pre-evolu- 

 tionary idea that species are normally con- 

 stant, uniform and stationary, so that evolu- 

 tion would need to be caused and conducted 

 by external agencies of the environment. 

 Though supported by no facts, the doctrine of 

 environmental causation is still being advo- 

 cated in many quarters in a manner strongly 

 reminiscent of the defense of special creation, 

 by Owen and Agassiz. The kinetic concep- 

 tion of evolution is in respect of causality as 

 different from environmental evolution as that 

 is from special creation, for it holds that spe- 

 cies are not made by the environment, but 

 that their development goes forward as a 

 manifestation of qualities inherent in their 

 very constitution. 



The progressive modiflcation of specific 

 groups of interbreeding organisms is as truly 

 a phenomenon, as much of a fact, as any 

 of our so-called factors, natural selection, 

 adaptation, variation, heterism, isolation, spe- 

 ciation, etc., which help to make up the evolu- 

 tionary drama. Evolution, in the kinetic ver- 

 sion, is not only the title of the play, but the 

 name of the principal role. It is no longer 

 restricted to the dialogue of the subordinate 

 players, like a mere ghostly abstraction. The 

 actions and relations of the various attendant 

 circumstances continue to give us very im- 

 portant aid in understanding the workings of 

 evolution, but they are no longer allowed to 

 explain it away into a nebulous compound of 

 definitions. Some of the persons are of the 

 immediate family of evolution, but others 

 have no direct relationship at all, though they 

 may appear often on the stage and perform 

 important parts. Thus natural selection is 

 the father of adaptation, but is related to evo- 

 lution only in the indirect, restraining ca- 

 pacity of guide and counselor. Evolution and 

 isolation are parents of speciation, but are 

 related only by this marriage, and had no 

 previous consanguinity. Environmental varia- 

 tion is at most only an uncle of evolution, not 

 the direct progenitor. The remaining minor 



