2j6 COOK 



appearance of similar mutations under diverse conditions may- 

 be accepted as proof that they were induced by the common 

 condition of inbreeding. Otherwise it would be necessary to 

 suppose that different topic factors have produced like results, 

 all of which shows the hopelessness of connecting mutations 

 with environment. Mutations represent abnormally accentuated 

 individual differences, and it seems not unlikely that most of them 

 follow lines of variation already established within the species. 1 

 It has been found in all the species thus far canvassed that a 

 few mutative tendencies are much more frequently shown than 

 the others. 



Nevertheless, it is not safe to assume that the same mutation 

 reappears even twice in identical forms. Whenever two similar 

 mutations of coffee, cotton, or Capsicum have been brought 

 together and compared they have always been found to be very 

 distinctly different, even more so than the unmutated individuals 

 of the uniform type from which they have arisen. 



3. EVOLUTION, SPECIATION AND ADAPTATION. 



One of the most frequent causes of confusion and error in 

 evolutionary thought is the failure to distinguish clearly between 

 evolution, speciation and adaptation; to distinguish, in other 

 words, between the process of evolution itself and two of the 

 relatively incidental results of environmental interference. 



As long as a group of organisms remains united so that all 

 its members interbreed freely with each other, evolution remains 

 a unit in the sense that the whole group, though it may be chang- 

 ing any or all of its characters, still keeps together and retains 

 its specific coherence. But if such a group be split into two or 

 more parts which do not interbreed, evolution has as many 

 separate courses, and the isolated parts attain differential char- 

 acters, or, to use the words of former days, new species origi- 

 nate. It is obvious, however, that the differentiation of the new 

 groups, while accomplished by evolution, is occasioned by isola- 

 tion. 2 The multiplication of groups, which as a process may be 



'The oranges, lemons and pomelos afford, according to Mr. W. T. Swingle, 

 many excellent examples of this parallelism of mutative variation. 



2 Confusion often creeps in at this point from the field of geology, for the 

 paleontological species is usually a random sample or section of the network of 



