ASPECTS OF KINETIC EVOLUTION 387 



was found in 1903 in Costa Rica. As ornamentals, some 

 variations offer new colors and greater abundance of flowers, 

 and the foliage and habit of the trees sometimes deviate strik- 

 ingly from the normal or parent form. Unfortunately, the 

 planters would find an advantage only in the direction of increas- 

 ing the number, size, or weight of the seeds themselves, and 

 they accordingly pronounce the new varieties worthless. 



Similar abrupt variations of many cultivated plants and animals 

 were studied and described by Darwin as "sports," but it was 

 also known to him that such variations are relatively infertile 

 and do not persist in the presence of the normal or less closely 

 inbred types, so that it has remained for Professor De Vries to 

 base upon such variations a general theory of evolution. The 

 variations, or sports, chiefly studied by Professor De Vries are 

 those of an evening primrose native in North America and 

 escaped from cultivation in Holland, and thus accidentally seg- 

 regated from the wild stock of its species. It belongs, like 

 the coffee, to a family in which there are specialized provisions 

 to assist cross-fertilization, so that the early manifestation of ihe 

 effects of inbreeding might be expected. 



The variations of (Enothera described by Professor De Vries 

 seem to be closely parallel to those of coffee ; most of them are 

 conspicuously deficient in reproductive fertility, and some are 

 quite sterile. This relative or complete sterility of sports, or 

 variations secured by inbreeding, warns us that evolutionary 

 inferences founded on this class of facts must be carefully 

 revised, since it is obvious that organisms notably deficient in 

 the power of reproduction can not be expected to have played 

 a large role in the process of organic evolution. Nature, like 

 the coffee-plantevs, requires seeds ; reproductive efficiency is the 

 first requisite of survival. 



A general evolutionary significance of the phenomena of muta- 

 tions becomes apparent when the facts are interpreted from 

 the standpoint of normal heterism, that is, as reactions from 

 the abnormal uniformity which is the first result of restricted 

 descent. The diversity of mutations is greater than the diver- 

 sity of normal heterism, but this is in entire accord with what 

 we know of other physiological reactions of organisms. Muta- 



