PREFACE. 



During the last three years the author has made three preliminary statements 

 of the law which is elaborated in this contribution. It belongs to an extended 

 treatise which the author has had in preparation since 1905. It is regrettably 

 incomplete in failing to give concrete examples from nature and from experiment 

 of each of the series of subordinate principles set forth. It seemed best, how- 

 ever, to publish the central principle, or Law of the Inseparable Factors, in its 

 present form rather than to delay longer for time and opportunity to publish the 

 concrete examples. 



The author takes advantage of the present opportunity to cite from his purely 

 biological contributions, 1 begun in 1889 and continued to 1912, which form a 

 progressive and more or less connected or consistent interpretation of the evo- 

 lution phenomena as observed by a palaeontologist. 



1 See full bibliography on page 307. 



275 



