786 



SCIENCE. 



[N. S. Vol. XXIII. No. 594. 



Thus it is needless to dispute and differ about 

 new G. Sp. and varieties. Every variety is a 

 deviation which becomes a Sp. as soon as it is 

 permanent by reproduction. Deviations in essen- 

 tial organs may thus gradually become N. 6. 

 Yet every deviation in form ought to have a 

 peculiar name, it is better to have only a generic 

 and specific name for it than 4 when deemed a 

 variety. It is not impossible to ascertain the 

 primitive Sp. that have produced all the actual; 

 many means exist to ascertain it: history, local- 

 ity, abundance, etc. This view of the subject 

 will settle botany and zoology in a new way and 

 greatly simplify those sciences. The races, breeds 

 or varieties of men, monkeys, dogs, roses, apples, 

 wheat . . . and almost every other genus, may 

 be reduced to one or a few primitive Sp. yet ad- 

 mit of several actual Sp. names may and will 

 multiply as they do in geography and history by 

 time and changes, but they will be reducible to a 

 better classification by a kind of genealogical or- 

 der or tables. 



My last work on Botany if I live and after 

 publishing all my N. Sp. will be on this, and the 

 reduction of our Flora from 8000 to 1200 or 1500 

 primitive Sp. with genealogical tables of the 

 gradual deviations having formed one actual Sp. 

 If I can not perform this, give me credit for it, 

 and do it yourself upon the plan that I trace. 



C. S. R. 



As we know, Rafinesque never worked out 

 the plan he thus had traced, nor was his 

 pathetic appeal to be given credit for it ever 

 entertained. Call (I. c.) regards Rafinesque 

 as a Lamarckian rather than a Darwinian, 

 but we are now, perhaps, warranted to ask 

 whether he was not really a de Vriesian. His 

 curious distinction between 'primitive spe- 

 cies ' ' and ' actual species ' is more pertinent 

 in this connection than his use of the word 

 * mutation,' though the coincidence is inter- 

 esting enough. His ' genealogical tables ' also 

 clearly foreshadow the ' phylogenetic tree,' 

 and altogether the whole letter reads singu- 

 larly prophetic. 



I am under obligation to Dr. Theodore Gill 

 for the references to Asa Gray and Darwin. 

 Leonhard Stejneger. 



U. S. National Museum, 

 Washington, D. C, 

 May 3, 1906. 



° In another article in the same journal, p. 

 173, he says that ' almost every genuine or 

 primitive species will be found to constitute a 

 peculiar genus.' 



THE INFLUENCE OF THE PLASTICITY OF ORGANISMS 

 UPON EVOLUTION. 



In their discussions of ' organic selection/ 

 Morgan, Osborn, Baldwin and others have 

 urged the importance of the plastic response 

 of the individual members of a species in 

 guiding the course of its evolution. I do not 

 see that one can doubt the reality of this in- 

 fluence, but as to the extent and exact char- 

 acter of the influence there seems room for 

 discussion. 



In the case of a species whose members are 

 highly plastic, responding promptly and ex- 

 tensively, in certain particular ways, to the 

 modifying influences of the environment, 

 those individuals in which similar adaptive 

 characters later appear as congenital varia- 

 tions will have but slight advantage over the 

 ontogenetically adapted, and selection must 

 he comparatively ineffective. The only ad- 

 vantage to the congenitally adapted will be 

 in the fact that in their early life they have 

 to pass through no period of education, and if 

 the ontogenetic adaptation of other individ- 

 uals be prompt and sufficient, it seems as if 

 the latter would be at comparatively slight 

 disadvantage. A high degree of plasticity 

 hinders evolution by selection, of characters 

 similar to those acquired by plastic response 

 to the environmental influences. 



In the case of a species whose members are 

 but slightly plastic, or are slow in their 

 adaptive response, the congenitally adaptive 

 may have a considerable initial advantage. 

 It is doubtful, however, if slight plastic re- 

 sponse will be highly effective in securing the 

 survival of the individuals until the species 

 could become congenitally modified in a simi- 

 lar way. 



So far, then, as a single set of characters 

 are concerned, we may say that a high degree 

 of plasticity wiU probably retard evolution as 

 much or more than it will guide, while slight 

 plasticity, allowing only imperfect ontogenetic 

 adaptation, may be ineffective in preserving 

 the species. The guiding effect of ontogenetic 

 responses upon the course of evolution can 

 hardly be both very extensive and intimate 

 (exact). 



