308 O. F. COOK 



consequence. Instead of preventing evolution by " swamping 

 effects" symbasic interbreeding is the true method or principle 

 by which evolution has been accomplished. 



Normal descent does not go forward in simple series of uni- 

 form individuals ; it is a broad network of closely interwoven 

 diversity. Once frayed by inbreeding into narrow, " unit- 

 character" shreds, the vital fabric is hopelessly weakened, and 

 the hereditary pattern distorted. The higher the organisms the 

 more acute the requirement of symbasic interbreeding, and the 

 more prompt and obvious the damage wrought by abnormal 

 segregation. To insist that mutational aberrations are suddenly 

 originated, genuine species, is the same as to assert that the 

 idiot offspring of cousins afford true examples of the steps by 

 which the perfection of the human race has been attained. 



Through long-continued selective inbreeding, cultivated plants 

 have been broken up into numerous local varieties of mutative 

 origin. These are frequentl}- quite as distinct from each other, 

 in the purely descriptive, taxonomic sense, as wild species in 

 nature, but their evolutionary status is very different. Wild 

 species in the truly normal and progressive (prostholytic ^) 

 evolutionary condition have a multifarious, intergraded indi- 

 vidual diversity, not to be found in mutative varieties. Species 

 which have not been domesticated too long show the inter- 

 mediate (hemilytic) condition of retarded evolution. Inbreed- 

 ing has induced an abnormal uniformity in which the degenera- 

 tive mutations begin to appear. 



Thus the coffee shrub has not yet become a mere congeries 

 of local varieties, but has an astonishing uniformity of type. 

 Seeds brought from remote regions and sown in the same place 

 produce plants of almost indistinguishable likeness. Of very 

 distinct, true-to-seed mutations of coffee, however, there is no 

 longer any lack, but very few of them have been preserved and 

 cultivated, because of their inferior powers of seed production 

 — a very practical proof of their degenerative nature. That 

 adverse conditions or abnormally restricted distribution may 

 bring about in nature evolutionary conditions analogous to those 

 of our domesticated plants, is, of course, to be expected, but 



' Stages of Vital Motion, Popular Science Monthly, 63 : 14. May, 1903. 



