THE ORIGINATION OF PARASITISM. 51 



that many features constructively adaptive may not be referred to the fac- 

 tors with which they interlock as causal agencies. 



The literature descriptive of structures and functional arrang-ements 

 which play some special part in the life of the species under the term 

 "adaptations" is voluminous. Purpose, useftilness, and direct adaptive 

 reactions are described in every striking- device that comes to the attention 

 of the observer. A writer may recognize the futility and inadequacy of the 

 teleological interpretation of organisms and still use its forms of reasoning 

 in text-books, lectures, and teaching, because it offers a short, easy method 

 of getting in touch with an audience, a practice open to much objection. 



Absolute candor compels us to admit that between the individually ac- 

 commodative or ontogenetic responses which might be carried over partially 

 to two or three generations and the complex mechanisms characteristic of 

 species which engage our attention as "adaptations," so called, there is 

 no definite connection, though we are willing to consider and to give the 

 utmost weight to circumstantial evidence bearing on the matter. The 

 single link which connects direct action of external agencies upon the 

 organisms with permanent changes are those in which climatic factors, 

 unusual forms of radiation, and solutions have shown to affect the germ- 

 cells in such a manner as to bring about permanently heritable alterations. 

 Such changes are not adaptive, although some of them result in greater 

 fitness to new environments, as has been proven in comparative tests of 

 parent and derivative in a series of habitats. These results, however, do 

 not justify the conclusion that all fitness has resulted from selection and 

 survival of germ- variations . (See recent views of L. Cu^not on Origin 

 of Species by Mutation, Science, vol. xxx, p. 768, 1909.) That somatic 

 accommodations and adjustments may be transmissible, the theory of 

 inheritance of acquired characters, the solace of the systematist, is a very 

 real possibility to the physiologist, as many facts suggest that the matter 

 may depend upon combination of circumstances not yet uncovered. 



The earlier results obtained by the establishment of acclimatization cul- 

 tures in connection with the Desert Laboratory justified the belief that the 

 subject was one amenable to direct experimentation, and that it might be 

 possible to obtain facts of importance by two different methods. One 

 would consist in testing the morphogenic and physiologic reactions of 

 plants to the action of climatic factors, especially with regard to their her- 

 itability. The second method of promise, which should be supplementary, 

 would involve the consideration of arrangements ordinarily termed adapta- 

 tions, of which various stages might be found in accessible types or species. 

 The induction of such adjustments in organisms not yet displaying them, 

 or the accentuation of the characters implied in forms in which they were 

 already present, would be taken as evidence of first-class importance. 



The lack of positive evidence as to the origination and perpetuation of 

 adjustments making for increased fitness is not to be regarded as singular 



