322 Cell as Basis of Organic Activity 



sideration of all known phenomena, he clearly began to see the relation- 

 ships of animals to one another. His most important contribution was 

 the influencing of later biologists and philosophers. These included 

 among others, Erasmus Darwin, the grandfather of Charles. He, too, 

 furthered the idea of evolution and held that organisms were affected by 

 their environment. The changes thus brought about, Erasmus Darwin 

 maintained, were inherited by the offspring. By this inheritance of 

 acquired characteristics, he thought new forms were brought into being. 

 A contemporary of Erasmus Darwin, Lamarck, likewise was convinced 

 of this inheritance. 



No adequate proof of the inheritance of acquired characters has ever 

 been given. Historically, the importance of this concept lies in show- 

 ing that evolutionary thought was growing in the minds of biologists of 

 the period preceding Charles Darwin. More important in its influence 

 on Charles Darwin was an essay by Malthus who was not a biologist 

 at all. As Malthus contemplated the growth of populations, he felt that 

 the number of individuals in the world was increasing geometrically while 

 the food supply was increasing arithmetically. Thus he foresaw an 

 eventual limiting of populations due to inadequate food supplies. It was 

 from the reading of this essay that Darwin conceived the important idea 

 of the struggle for survival. 



The concept of evolutionary change had a long period of growth 

 in the thoughts of Darwin. When he was but a very young man, he 

 undertook a four-year voyage around the world as biologist on the ship, 

 the Beagle. During this trip, the stimulus of so many new lands with 

 their varied plants and animals affected him profoundly. He visited 

 many islands, observing that their fauna was related to that of the main- 

 land. Also of great importance in the development of his ideas was his 

 collecting of fossils and his study of geological strata in South America. 

 The ideas thus gathered gradually took form in his thinking, resulting in 

 his conceiving the theory of organic evolution as stated in The Origin 

 of Species published in 1859. 



Shortly before Darwin was ready to publish his thesis, he received 

 a letter from the naturalist Wallace who was in the East Indies. Wal- 

 lace had spent most of his life observing animals and plants in many 

 areas, and he, too, was struck by the multitude of forms and their re- 

 lationships. He, too, had conceived the idea of organic evolution. Dar- 

 win, in a characteristic manner, did not burn Wallace's letter^ rather 

 be made the pronouncement a joint one. 



