vi FORAMINIFERA OF THE CRAG. 



tigatioiis connected with animals of very low organization, that they are not to be regarded 

 as of the same importance as similar, but more permanent, marks would be in higher 

 animals. The difficulty in determining species is enhanced by the fact, that, whilst on 

 the one hand several distinct species may each present varieties so similar that they may 

 be easily confounded, on the other hand the extreme variations in sub-specific forms may 

 at first sight often appear of generic value.^ 



With these preliminary remarks we may proceed to the critical examination of the 

 generic and specific forms which have been found in the Crag — endeavouring to distin- 

 guish the essential from the non-essential characters, the typical from the aberrant, the 

 specific from individual modifications, and holding in view the same principles of investi- 

 gation, the adoption of which has led, dm-ing recent years, to so great an increase of our 

 knowledge of the group, at the hands of Williamson, Carpenter, Reuss, and others. 



1 We have sometimes thought that a passage in Whewell's ' Philosophy of the Inductive Sciences,' 

 written, it is true, in reference to a far difl'erent subject, might have been written, mutatis mutandis, with almost 

 equal truth of the nomenclature of the Foraminifera. Speaking of Haiiy's nomenclature of the crystals of calcite, 

 he says — " The want of uniformity in the origin and scheme of these denominations would be no valid objection 

 to them if any general truth could be expressed by means of them ; but the fact is, there is no definite dis- 

 tinction of these forms. They pass into each other by insensible gradations, and the optical and physical 

 properties which they possess are common to all of them. And, as a mere enunciation of the laws of 

 forms, this terminology is insufficient. Thus it does not at all convey the relation between the bisalteme 

 and the binoternaire ; the former being a combination of the metastatique with the prismatique ; the latter 

 of the metastique with the contrastante ; again, the contrastante, the mixte, the cicboide, the contraciSe, 

 the dilatde, all contain faces generated by a common law, the index being respectively altered, so as to be 

 in these cases, 3, f, f, f , f ; and this, which is the most important geometrical relation of these forms, is 

 not at all recorded or indicated by the nomenclature." 



Note. — A very valuable memoir on the Enghsh and Belgian Crag formations, by Mr. R. Godwin-Austen, 

 F.R.S., has just appeared in the ' Quart. Journ. Geol. Soc. London,' vol. xxii, part 3 (No. S/), p. 229. &c. 

 It is full of important facts and sound philosophic disquisitions. — August, 1866. 



