GENERAL INTRODUCTION. 183 



in the immense aggregation of individuals they contain, thus presenting the materials 

 for a most full and complete investigation into that hitherto comparatively neglected 

 subject, the range of variation within the limits of species. And the great value of 

 Mr. PARKER'S collection lies in his having followed out this inquiry (first suggested to 

 him by myself as the result of my examination of the other two collections) in regard 

 to a much larger number of species, and with materials brought together from a 

 much wider geographical area. 



The question has been anxiously considered by me, in what mode I might render 

 these materials most beneficial to the progress of science ; and I have come to the 

 conclusion, with the full concurrence of some of the most eminent Naturalists both 

 of this country and of the continent, that I should be doing the most acceptable 

 service, by instituting a searching investigation into the entire history of such typical 

 forms of this remarkable group, as should be most fitted to afford satisfactory data 

 for reasoning with regard to the rest ; including in this history, a minute exami- 

 nation of the structure, not only of the testaceous skeletons, but also (where this 

 might be possible) of the soft animal body ; a careful survey of the differences of form 

 and aspect presented at different ages, so as to enable the history of any individual to 

 be traced from its origin to its decline; a comparison of the variations both in 

 external form and internal structure, presented by different specimens, sufficiently 

 extensive to admit of the determination how far these variations are of value as 

 specific characters, or how far they must be accounted merely individual departures 

 from the ordinary type ; a like comparison between the series collected in different 

 geographical areas, so as to afford a safe basis for the determination of the range of 

 the species, and the amount of its variation in space; and a further extension of this 

 comparison to similar series obtained from the various geological strata in which the 

 like forms may present themselves, so as to ascertain the range of the species and the 

 extent of its variation in time. And if I should seem, in following out this plan, to 

 have erred on the side of over-minuteness, I trust to receive credit for the real motive 

 which has induced me to bestow so much elaboration on the work I have under- 

 taken, namely, the desire to furnish a thoroughly secure foundation, on the basis 

 of which the labours of others, in whatever department of the inquiry, may be safely 

 utilized in building up a complete and harmonious superstructure. 



It had been my intention to preface the account of my own Researches, with a 

 summary of the History of our knowledge of the group generally. This subject, 

 however, has been so fully and satisfactorily worked out, in two of the most recent 

 treatises on the subject, that of MM. D'ARCHIAC and HAIME on Nummulites*, and 

 that of Professor SCHULTZE on certain forms of existing Foraminifera-j~, the latter 



* See their " Monographic des Nummulites," forming part of their " Description des Animaux Fossiles du 

 Groupe Nummulitique de 1'Inde," Paris, 1853. 



t Cber den Organismus der Polythalamien (Foraminiferen) nebst Bermerkungen iiber die Rhizopoden im 

 allgemeinen. Leipzig, 1854. 



2 u 2 



