viii PREFACE. 



into a greater variety of forms than the fabled Proteus, laying hold of its food without 

 members, swallowing it without a mouth, digesting it without a stomach, appropriating its 

 nutritious material without absorbent vessels or a circulating system, moving from place to 

 place without muscles, feeling (if it has any power to do so) without nerves, propagating 

 itself without genital apparatus, and not only this, but in many instances forming shelly 

 coverings of a symmetry and complexity not surpassed by those of any testaceous animals. 



Again, there are certain peculiarities about the Foramini/era which makes this group 

 singularly adapted for that kind of comparison, at once minute and comprehensive, amongst 

 large numbers of individual forms, which should be the basis of all Zoological systematization. 

 The size of the greater part of these organisms is so small, that many hundreds, thousands, or 

 even tens of thousands of them, may be contained in a pill-box ; and yet it is usually not too 

 minute to prevent the practised observer from distinguishing the most important peculiarities 

 of each individual by a hand-magnifier alone, or from dealing with it separately by a very 

 simple kind of manipulation. Hence the Systematist can easily select and arrange in series such 

 of his specimens as display sufficient mutual conformity, whilst he sets apart such as are tran- 

 sitional or osculant ; and an extensive range of varieties may thus be displayed within so small 

 a compass, that the most divergent and the connecting forms are all recognisable nearly in 

 the same glance. I am not acquainted with any other group of natural objects, in which such 

 ready comparison of great numbers of individuals can be made ; and I am much mistaken 

 if there be a single specimen of plant or animal, of which the range of variation has been 

 studied by the collocation and comparison under one survey of so large a number of specimens 

 as have passed under the review of Prof. Williamson, Messrs. Parker and Rupert Jones, and 

 myself, in our studies of the types to whicli we have respectively given our principal atten- 

 tion. The extraordinary diversity thus found to exist among organisms which, from the 

 intimacy of the relationship evinced in the gradational character of those differences as well 

 as in the variations observable between the several parts of one and the same organism, must 

 in all probability have had a common origin, seems to me unmistakeably to indicate that the 

 wide range of forms which this group contains is more likely to have come into existence as a 

 result of modifications successively occurring in the course of descent from a small number of 

 original types, than to have originated in the vast number of distinct creations which on the 

 ordinary hypothesis would be required to account for it. Hence I cannot but believe that any 

 systematic arrangement of Foraminifera will be of real value only in so far as its basis is laid 

 in a thorough knowledge of the nature and extent of those variations which every chief modifi- 

 cation of this type shows itself so peculiarly disposed to exhibit, and as, in building it up, the 

 idea of natural affinity is accepted as expressing not only degree of mutual conformity, but 

 actual relationship arising from community of descent more or less remote. For the occurrence 

 of endless gradational departures from any types which we may assume as fixed, and of links 

 of connection between such as present the best-marked differentiations, seems to me to point 

 unmistakeably to this as the only means of escape from that difficulty of indefinite multiplica- 



