TRUE DARWINISM 163 



Of course they have always been plentiful, but his attention 

 was not drawn to them ; yet, strange to say, it was due to the 

 "direct action of the environment" that all our domesticated 

 animals and cultivated varieties have arisen. As his mind ran 

 on " Selection " he overlooked " Adaptation ". 



In discussing any question as to the origin of species the 

 first question to ask is, What is a Species ? Darwin himself 

 did not define it, but rather left his readers to infer or draw 

 their own conclusions as to what he meant by the term. The 

 following, however, will answer the question as systematists 

 regard it. A species is known by a collection of relatively 

 constant, morphological characters. In the case of plants these 

 may be taken from the forms of any or all of their organs, i.e., 

 roots, stems, leaves, flowers, fruits and seeds. 



Whenever a plant is found to depart somewhat but con- 

 stantly from the typical description of the species, in any one or 

 more of its characters, such is called a " variety," and varieties, 

 according to Darwin, are "incipient^ species". 



The second question to ask is, What causes organisms to 

 vary ? Most biologists appear to be agreed that the cause is, 

 primarily at least, due to the environment taken in its widest 

 sense. Thus, Dr. Weismann says : " We are driven to the 

 conclusion that the ultimate origin of hereditary individual 

 differences lies in the direct action of external influences upon 

 the organism ".^ If the surroundings remain permanently the 

 same then there is little or no inducement for the organism to 

 change. Thus it has been noticed that the flowers found in 

 wreaths in the Egyptian tombs are exactly like those of to-day, 



^ I doubt the correctness of this word. The difference between a 

 "variety" and an allied "species" is one of degree, it is true, but the 

 origin of both is due to the relative amount of the "direct action" of 

 the environment together with the response to it. If this be comparatively 

 slight a variety results ; but as long as it remains, generation after genera- 

 tion, under the same conditions it will not advance to acquire a specific 

 form, but remains permanently a variety. Many such are recorded in 

 Floras. 



"^Essays on Heredity, etc., Eng. trans., p. 279. 



