CONCLUDING STJMMAET : EXTENT OF EANGE OF VAEIATION. 579 



And I have now to show that the results of my inquiries in regard to such typical forms 

 of Foraminifera as have passed under my review, are in complete accordance with those 

 obtained by other naturalists who have proceeded upon the like method, that of the 

 comparison, not of selected specimens, but of entire gatherings over extended areas and 

 through various geological epochs. 



253. Long ago did those excellent observers MM. FICHTEL and MOLL (1803) manifest 

 a clear perception of the wide range of variation to which certain types of Foraminifera 

 are liable, and give admirable descriptions and figures of such varieties. But their 

 views were too philosophical for the species-making systematists of their time : thus we 

 find MONTAGU remarking of the forms which they ranked under the designation of Nau- 

 tilus (now Cristellaria) calcar, " If these can be admitted as the same species, we may 

 bid adieu to specific definition;" whilst out of the same series DENTS DE MONTFORT con- 

 structed no fewer than nine genera. It has been most unfortunate for the advance of 

 this inquiry, that M. D'ORBIGNY should have prosecuted it under the influence of those 

 ideas in regard to the differentiation of specific types, which he brought to the study of 

 Foraminifera from that of the testaceous Mollusks to which he originally regarded them 

 as allied; and that the influence of his comprehensive labours and high reputation 

 should have given to his views, alike on the detailed arrangement and on the general 

 classification of this group, a currency to which their entire inconsistency with its 

 natural affinities entirely negatives their claim. It was in studying one of the simplest 

 types of this series, that Professor W. C. WILLIAMSON was led (1847) to perceive " the 

 extraordinary capacity for variation which Lagence exhibit in different states and ages ; 

 extreme forms which appear to be very distinct from one another being connected 

 together by specimens of an intermediate aspect to an extent only to be believed by 

 those who examine a large series of specimens side by side*." And he adduced strong 

 evidence, not only that most if not all of its reputed species are only varieties, but that 

 the difference which separates the genus Lagena from Entosolenia, viz. that the neck 

 of the flask-shaped body is prolonged inwards in the latter, instead of outwards as in the 

 former, may be merely varietal. A like conclusion, strengthened by the results of his 

 and my researches in regard to other types, Professor WILLIAMSON has extended to Fora- 

 minifera generally, in his beautiful Monograph of the Recent Foraminifera of Great 

 Britain (1857). "It may now be regarded," he says, "as an established truth, that 

 most of the external characters on which both earlier and later writers relied for distin- 

 guishing their species, possess but little value. The direction of growth in these shells, 

 and the sculpturing of their exteriors, are alike influenced by age and local circum- 

 stances; hence a dissimilarity between the different stages in the development of the 

 same individual, such as finds few parallels amongst the Mollusca with which Concho- 

 logists have so long identified them." Again, he remarks, " Nothing is easier than to 

 throw the Foraminifera obtained by dredging over some limited area into defined groups, 

 each of which has apparently a specific value. But as we extend our researches to more 

 distant localities, new and intermediate forms perplex our minds as to what are the same 



* Annals of Natural History, Jan. 1848, p. 10. 

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