CiiAr. X. FOKMS OF LIFE CHANGING. 3O3 



plex cuntinoencies, on which ilic existence of e;ich species de- 

 pends. If "SVC for<ret, for an instant, that each species tends to 

 -Ticreasc inordinately, and that some check is always in action, 

 yet seldom perceived l)y us, the whole economy of Nature will 

 be utterly obscured. Whenever we can precisely say why this 

 species is more alnmdant in individuals than that ; why this 

 species and not another can be naturalized in a given country; 

 then, and not until then, we may justly feel surprised why we 

 cannot account for the extinction of any j)articular species or 

 any grouj) of species. 



On the Forms of Life changlnff almost simultaneously 

 throughout the World. 



Scarcely any jialeontological discovery is more striking 

 than the fact that the forms of life change almost simultane- 

 ously throughout the world. Thus our European Chalk for- 

 jnation can be recognized in many distant parts of the world, 

 imder the most different climates, where not a fragment of the 

 mineral chalk itself can be found ; namely, in North America, 

 in equatorial South America, in Tierra del Fuego, at the Cape 

 of Good Hope, and in the peninsula of India. For, at these 

 distant points, the organic remains in certain beds present an 

 unmistakable resemblance to those of the Chalk. It is not that 

 the same species are met with ; for in some cases not one 

 species is identically the same, but they belong to the same 

 families, genera, and sections of genera, and sometimes arc 

 Kimilarly characterized in such trilling points as mere superficial 

 sculpture. Moreover, other forms, which are not found in the 

 Chalk of Europe, but which occur in the formations either above 

 or below, occur in the same order at these distant points of the 

 world. In the several successive paleozoic formations of Rus- 

 sia, Western Europe, and North America, a similar parallelism 

 in the forms of life has been observed by several authors : so it 

 is, according to Lycll, with the several European and North 

 American tertiary deposits. Even if the few fossil species 

 which are common to the Old and New Worlds were kept 

 wholly out of view, the general ])arallelism in the successive 

 forms of life, in the paleozoic and tertiary stages, would still 

 be manifest, and the several formations could be easily corre- 

 lated. 



These observations, however, relate to the marine inhabit- 

 ants of the Avorld: we have not sufTirient data to judge whelhcr 



