GENUS ORBITOL1TES: CONCLUDING REMARKS. 229 



aquilina has a different name in almost every country in the world. It has been 

 through reliance on such ignorant determinations, most of them proceeding on the 

 notion that " the plants (or animals) of newly-discovered, isolated, or little-visited 

 localities must necessarily be new," that the doctrine of the universal distinctness of 

 the species of the New World from those of the Old, and of those of the Southern 

 from those of the Northern Hemisphere, has attained a very wide currency amongst 

 Naturalists, and is still obstinately persisted-in by some, in defiance of ample evidence 

 to the contrary*. (5) Lastly, not only has the limitation of the comparison among 

 Fossil types, to a small number of individuals, led to the excessive multiplication of 

 species in the forms that are furnished by the same strata ; but the same habit of 

 relying on minute differences, without attention to osculant characters, has given 

 rise to that disposition to regard the species of successive formations as necessarily 

 different, which is introducing the greatest confusion into geological and palaeonto- 

 logical determinations of every kind. How an extended comparison of individual 

 forms tends not only to reduce the number of reputed species, but to establish the 

 continuity of the same specific types fiom one stratum to another, will be remarkably 

 seen when the laborious researches of Dr. WRIGHT of Cheltenham on the Cidarites of 

 the Liassic and Oolitic formations shall have been made public. 



76. Another general consideration of some interest, appears to me naturally to 

 connect itself with the foregoing history, namely, that the lower the general plan 

 of organization of any being (that is, the greater the prevalence of ' vegetative' or 

 ' irrelative' repetition in its different parts), the more is that plan liable to be modified 

 by slight differences in external conditions, and the wider, therefore, may we expect 

 its range of variation to be, if it be disposed to vary at all. In some instances, it is 

 true, there appears (as in many higher forms of organization) to be an absolute 

 incapacity for any such variation ; and a limitation of the geographical and geolo- 

 gical distribution of the species results from its want of power to exist under any 

 great diversity of external conditions. But when the same general type of organiza- 

 tion is found to prevail extensively both in space and in time, it may, I think, be 

 safely regarded as probable, that that type has within itself the power of accommo- 

 dation to a considerable diversity of external conditions ; and hence that in the com- 

 parison of individuals, differences of conformation should be considered as of less 

 account towards the establishment of specific distinctions, than they are when there 

 is an obvious restriction of the type to a limited Geographical area or a' particular 

 Geological epoch. 



77- In the foregoing communication, I have thought it right not only to make 

 known the results of my researches, but so to develope my plan of investigation, that 

 the value of those results may be duly estimated. In the memoirs which I trust to be 



* " Thus as long ago as 1814, Mr. ROBERT BROWN gave a list of 150 European plants common to Australia 

 and Europe. The identity of many of these has repeatedly been called in question, but almost invariably 

 erroneously ; added to which, more modern collectors have greatly increased the list." HOOKER, op. cit. p. 18. 

 MDCCCLVI. 2 H 



