THE BIOLOGICAL RELATIONS OF FOSSILS. 57 



CHAPTER VI. 

 THE BIOLOGICAL RELATIONS OF FOSSILS. 



Not only have fossils, as we have seen, a most important 

 bearing upon the sciences of Geology and Physical Geography, 

 but they have relations of the most complicated and weighty 

 character with the numerous problems connected with the 

 study of living befngs, or in other words, with the science of 

 Biology. To such .an extent is this the case, that no adequate 

 comprehension of Zoology and Botany, in their modern 

 form, is so much as possible without some acquaintance with 

 the types of animals and plants which have passed away. 

 There are also numerous speculative questions , in the domain 

 of vital science, which, if soluble at all, can only hope to find 

 their key in researches carried out on extinct organisms. To 

 discuss fully the biological relations of fossils would, there- 

 fore, afford matter for a separate treatise ; and all that can be 

 done here is to indicate very cursorily the principal points to 

 which the attention of the palseontological student ought to 

 be directed. 



In the first place, the great majority of fossil animals and 

 plants are "extinct" that is to say, they belong to species 

 which are no longer in existence at the present day. So far, 

 however, from there being any truth in the old view that there 

 were periodic destructions of all the living beings in existence 

 upon the earth, followed by a corresponding number of new 

 creations of animals and plants, the actual facts of the case show 

 that the extinction of old forms and the introduction of new 

 forms have been processes constantly going on throughout the 

 whole of geological time. Every species seems to come into 

 being at a certain definite point of time, and to finally dis- 

 appear at another definite point ; though there are few in- 

 stances indeed, if there are any, in which our present know- 

 ledge would permit us safely to fix with precision the times of 

 entrance and exit. There are, moreover, marked differences 

 in the actual time during which different species remained in 

 existence, and therefore corresponding differences in their 

 "vertical range," or, in other words, in the actual amount and 

 thickness of strata through which they present themselves as 

 fossils. Some species are found to range through two or even 

 three formations, and a few have an even more extended life. 

 More commonly the species which begin in the commence- 



