GENUS ORBITOLITES: CONCLUDING REMARKS. 227 



with which we have a tolerable acquaintance: and Thirdly, that certain general 

 principles evolve themselves as results of these investigations, which are quite as 

 applicable to every other department of Biological Science, as they are to the single 

 case of the Orbitolite. 



72. It has been shown that a very wide range of variation exists among Orbitolitex, 

 not merely as regards external form, but also as to plan of development ; and not 

 merely as to the shape and aspect of the entire organism, but also with respect to the 

 size and configuration of its component parts. It would have been easy, by selecting 

 only the most divergent types, from amongst the whole series of specimens which I 

 have examined, to prefer an apparently substantial claim on behalf of these to be 

 accounted as so many distinct species ; and I could thus have easily created an almost 

 indefinite number of such species. But after having classified the specimens which 

 could be arranged around these types, a large proportion would yet have remained, 

 either presenting characters intermediate between those of two or more of them, or 

 actually combining those characters in different parts of their fabric; thus showing 

 that no lines of demarcation can be drawn across any part of the series, that shall defi- 

 nitely separate it into any number of groups, each characterized by features entirely 

 peculiar to itself. Thus, then, we see that the real relationship of the different types 

 to each other, can only be determined by the careful comparison of a very large 

 number of individuals obtained from as many different sources as possible ; a process 

 which is too frequently neglected by Systematists, many of whom erect species, and 

 even genera, without the least care to determine, by any such process, the real value 

 of the distinctions by which they characterize them. 



73. The right mode of proceeding in every other department of Natural History, 

 must be that which has thus been proved to be the only reliable method in this ; and 

 I venture, therefore, to lay down the following general Canons, deduced from the 

 results of the preceding investigation; which will, I think, be found accordant with 

 the experience of all soundly-judging Naturalists, although they have not yet, so far 

 as I am aware, received a formal expression. 



74. To become fully acquainted with the Natural History of any Species, it is 

 requisite ; ( 1 ) to study not only its external conformation, but also its internal organ- 

 ization; by which alone can the value of superficial resemblances or differences be 

 duly estimated ; (2) to trace out its entire developmental history, so that the true 

 relationship of individuals in different stages of evolution may be appreciated ; 

 (3) to compare together a large number of specimens taken from any one locality, 

 in order to ascertain what is the range of its variation under nearly identical condi- 

 tions ; (4) to search out its whole Geographical distribution, and to bring into mutual 

 comparison large numbers of specimens from the remotest regions, as well as from 

 all the intermediate areas over which it spreads, in order to determine the range of 

 its variation under the most diverse conditions ; and (5) to follow the same course of 

 comparison throughout its Geological distribution, still relying only on the informa- 



