91 



By showing that the years devoted by the horticulturist to 

 "fixing" new garden varieties have for their purpose the elimi- 

 nation of the effects of " vicinism," /. e., the chance crosses with 

 neighboring species or varieties, and by distinguishing between 

 ever-sporting varieties and thpse which possess only an ordinary 

 degree of fluctuating variability, the way has been cleared for a 

 proper appreciation of the true relations between the garden and 

 nature. It is doubtful however whether physiologists will agree 

 that the cases of "double adaptations" in nature, and the rela- 

 tion of juvenile to adult leaf-characters, are to be classed with the 

 ever-sporting varieties of the garden, for in the former cases def- 

 inite laws of occurrence of the alternative characters are discern- 

 ible, while in the ever-sporting varieties no such laws have yet 

 been detected and they seem in many instances to be closely 

 related to fluctuating variations. 



The book is divided into six sections. After an introductory 

 lecture on the theories of evolution.and methods of investigation, 

 the conception of elementary species as distinct from systematic 

 species is developed, and a definite and distinctive significance is 

 attached to the term, "variety," which is quite different from its 

 usually loose usage for any assemblage of forms, less^ extensive 

 than the systematic species. A variety as conceived by de Vries 

 is not qualitatively like a species, being distinguished from the 

 species to which it belongs and from which it has been derived in 

 the possession or lack of some, single definite character, or two 

 or three single characters at most while species differ from one 

 another in almost every character. The several different kinds of 

 varieties, progressive, retrogressive, degressive, and ever-sporting, 

 are thoroughly considered, along with the included subjects of 

 latency and atavism. 



The fifth section deals with mutations, the evening-primroses 

 naturally having an important place, but the number of other 

 fully authenticated cases described will doubtless give surprise to 

 some readers who may have thought that the mutation theory 

 rests only on the behavior of Onagra Lamai'ckiana. 



The last section is devoted to individual and partial variability 

 or "fluctuation" as it is called. This process, which has. been 





