CHANGING OF SPECIES. 



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CHANGING OF SPECIES. 

 By G. F. Scott-Elliot, M.A., B.Sc, F.L.S. 

 [Being the sixth 'Masters Lecture/ delivered March 14, 1911.] 



As I tried to show in the previous paper, seedhngs in most respects 

 resemble their parents. If their parents are strong, vigorous, and 

 hardy, then the seedhng is healthy and well-doing. If the father and 

 mother are weakly, then the descendants also will be weak, wanting in 

 virility and very likely unable to survive one or other of the infantile 

 maladies usual to its species. 



When a seed is well formed, weighty, and plump and packed full 

 of nutritious substances, the young plant will have the best possible 

 start in life; it will in all probability keep indefinitely the lead due to 

 its excellent outfit and will probably remain always ahead of those of 

 its competitors who were not in their infancy so well provided for. 



That this is true is a matter, as I tried to show, not only of common 

 knowledge but of common sense, and the truth of this view is sup- 

 ported by whole arrays of carefully conducted experiments carried out 

 by observers of acknowledged reputation. 



Under ordinary conditions a young plant inherits not only its 

 parents' constitution but also their conditions of life. It lives in 

 essentially the same climate, it has to withstand the same sort of 

 enemies, whether fungi or insects, which assailed its forefathers. It is 

 subject to April showers, May frosts, and June sunshine quite similar 

 to those which have continually affected not only its parents but their 

 ancestors for thousands of years. 



The continuity of species under continuously similar conditions is 

 precisely what we should expect, and although this apparent immobility 

 has often been used as an argument against possible changes of type, 

 it has really nothing to do with the real question. 



The real point is whether a distinct change of conditions can alter 

 in any way the characteristics of a species. 



A flowering plant is a complex organism with habits and rhythms 

 strongly fixed and dependent on complicated series of cell divisions ; 

 the change must be of the most radical and ruthless character if all 

 these successions and their effects are to be suddenly altered. 



In the simplest unicellular organisms such as bacteria and yeasts, 

 the dependence of the character of the organism upon its environment 

 is perfectly obvious. Such organisms are indeed usually classified by 

 their reactions and behaviour in the various media in which they 

 can be cultivated. 



Under skilful treatment bacteria originally of the most dangerous 

 character can be made perfectly innocuous or, if one desires to do 

 so, they can be so altered that they are infinitely more virulent and 



