130 PROGRESS OF SCIENCE. 



classifying them in accordance with their anatomy, and 

 divided them into classes, orders, and genera being the first 

 naturalist to begin a classification with the simplest and least 

 highly organised animals. The great work of his life, how- 

 ever, had by far more importance than all this series of 

 laborious researches, and was certain to exert paramount 

 influence over scientific philosophy for all times. His process 

 of classification seems logically to have convinced him (1801) 

 that, acting by law, nature commenced with the simplest 

 types, and that from these types had sprung an ever in- 

 creasing variety of species branching off from one another, 

 so that the present plants and animals are the outcome of 

 those of past geological eras. Therein lay the whole subject 

 of evolution versus creation a momentous subject which was 

 destined, after Charles Darwin, to force human thought into 

 new regions. From this brief statement it is easy to see 

 that none could have more influence than Lamarck over the 

 modern school of evolutionists. His work, " Philosophic 

 Zoologique," which Robert Chambers popularised in " Vestiges 

 of Creation" (1844), has shaped evolutionary thought and 

 produced a decisive impression upon scientific men. The 

 last thirty years of his life were devoted to the elucidation 

 of the problem of origin of species. The core of his teaching 

 lies in the formulation of the idea that gradual modification 

 from one primordial type has produced them all, and he 

 extended this doctrine to the inorganic world alterations 

 being in all cases and in every sphere the result of law. 

 Anticipating Lyell, he even held that the ordinary process 

 of natural laws was sufficient to account for all the phe- 

 nomena presented by the earth's crust. He held the means 

 of animal modification to have been, and to be due, not to 

 differences and changes of habitat only, as is often said of 

 him, but (i) to the direct environment or physical conditions 

 of life., of which climatic and geographical changes form only 

 a part ; (2) to the blending, or separating, or crossing of 

 formerly existing types ; (3) to the effects of habits, and 

 hence to the use and disuse of certain organs and limbs. 

 The "use and disuse" theory has been considered as of 

 paramount importance by C. Darwin and Herbert Spencer. 



