ex; PEOCEEDIKGS OF THE GEOLOGICAL SOCIETY. 



His principal attention, as he himself observes, has been directed 

 to the physical condition of the globe, and to everything which in 

 one way or another is connected with biological phenomena. 

 These questions are often neglected by naturalists, who, devoting 

 themselves too exclusively to the examination of species, lose 

 sight of those external causes which even at the present time, 

 either on the surface of the continents, or in the depths of seas 

 and lakes, act directly on the functions and characters of organs, 

 and consequently on those of the animals and vegetables them- 

 selves. 



But, interesting as is the whole work, I think the two first 

 chapters are particularly deserving our a,ttention, but I can only 

 briefly indicate tlie subjects of which they treat. The first chapter 

 discusses the origin and development of organic beings, and 

 tbeir successive forms. The author shows that the organization of 

 the most ancient forms with which we are acquainted, as prescribed 

 in the oldest sedimentary rocks, as well as those of the present 

 day, entirely destroys the hypothesis that the more perfect forms 

 were derived, by secular modifications, from preexisting and less- 

 developed species. The succession of these forms indicates a con- 

 stant progress and a uniform plan, which cannot be the mere re- 

 sult of eliance ; and whether we look at the great assemblages of 

 forms in any given period, or the appearance and extinction of 

 species in time, we must recognize a law which regulates their 

 relative position, and maintains a certain equilibrium. And al- 

 though we may never arrive at the perfect knowledge of the law 

 whicb regulated the creation and the existence and final dying out 

 of many forms, Ave can trace many of the physical changes in the 

 conditions of life which have infiuenced the existence of organic 

 beings. He then discusses the three principal kinds of causes 

 which mainly infiuenced the conditions of life before the present 

 epoch, namely, chemical, physical, and meteorological. 



The second chapter is devoted to the discussion of the question 

 of species. Varied are the opinions on this subject. It is the 

 great stumbling-block of naturalists. M. d'Archiac endeavours 

 to point out and to discuss the principal opinions which have been 

 enunciated, the grounds by which they have been supported, and 

 to justify those which appear to him most tenable. After giving 

 the general views of the most distinguished naturalists on this 

 subject, the author proceeds to discuss in more detail the works 

 of Mr. Darwdn and of M. Godron, particularly the former. This 

 is done with great fairness, although he cannot adopt his conclu- 

 sions ; for M. d'Archiac declares himself a full believer in the 

 immutability of species, and having declared himself against the 

 doctrine of variability or transmutation of species, first brought 

 forward, on scientific grounds, by Lamarck, he maintains that 

 the balance of all observations proves that the idea of fixity of 

 species is founded on the study of nature. This must be distin- 

 guished from their perpetuity. They die out and are succeeded by 

 others ; but we have yet to learn the laws which have regulated 



