640 HISTORY OF SCIENCE. 



This theory has, like others already noticed in these pages, met with 

 abundant opposition. The literature of the subject, though extending 

 over only twenty years, is extensive enough to occupy a whole library. 

 As many of the works relating to " Darwinism " are very popular and 

 accessible books, we shall here merely quote two brief and clear state- 

 ments of the Theory of Natural Selection. The first is from St. George 

 Mivart's " Genesis of Species," where it runs thus : 



" Every kind of animal and plant tends to increase in numbers in a geometrical pro- 

 gression. 



" Every kind of animal and plant transmits a general likeness, with individual diffe- 

 rences, to its offspring. 



' ' Every individual may present minute variations of any kind and in any direction. 

 " Past time has been practically infinite." 



Mr. Wallace presents a demonstration of the Origin of Species by 

 Natural Selection in a tabular form nearly like the following : 



PROVED FACTS. NECESSARY CONSEQUENCE. 



(Taken in the next following deduction as 

 a "proved fact.") 



1. Rapid Reproduction of Organisms. \ 3. STRUGGLE FOR EXISTENCE; the 



2. Total Number of Individuals Sta- \ deaths on the average equalling the 



tionary. } births. 



3. Struggle for -Existence. ) SURVIVAL OF THE FITTEST, or 



4. Heredity with Variation or general V Natural Selection . 



likeness with individual differences. ) 



> 7. CHANGES OF ORGANIC FORMS, to 



5. Survival of the Fittest. keep them in harmony with the 



6. Changes of External Conditions, I changed conditions. As these never 



universal and unceasing. recur, so the divergences of organic 



J form are permanent. 



According to the Theory of Natural Selection, feline races did not 

 obtain their retractile claws by their habits, or their efforts, or their 

 desires, but because in the struggle for existence among less highly 

 organized forms, those survived which were best able to seize upon 

 their prey. This " survival of the fittest " is a very different explana- 

 tion of the changes in organisms from that advanced by Lamarck 

 (page 396). 



The Theory of the Descent of animal and vegetable species from 

 common and simple prototypes, as held by Lamarck and Goethe, when 

 worked out and based on the Theory of Natural Selection, may be 

 appropriately called the Theory of Development. Its opposite is the 

 view which regards species as eternal and invariable, and this view has 

 been stoutly defended against Darwin and his numerous supporters. 

 Indeed, the unqualified and unopposed acceptance of any important 

 theory would, as the reader of these pages must already know, be a 

 new thing in the history of science. Nevertheless, the Development 

 Theory must be considered as a good working hypothesis, now accepted 



