58 
THE VOYAGE OF H.M.S. CHALLENGER. 
general or extended criticism. The Sub-order Testacea, which comprises all testaceous 
Rhizopods, whatever the nature of their investment, is divided into two Tribes — 
Imperforata and Perforata. The former of these terms is employed in a much wider 
sense than in any previous classification, and is made to include (1) all Rhizopods with 
chitinous tests, whether the pseudopodia are lobose or reticulated ; (2) the Porcellanea ; 
and (3) a portion of the Arenacea. To the Lituolidce no distinct position is assigned, 
but part of them are placed with the hyaline forms they most nearly resemble in shape 
(usually inserted as “ allied genera ”), and the rest are similarly annexed to porcellanous 
Families such as Peneroplidina. Turning to the Perforata, there is little to notice in the 
arrangement of the earlier groups, which is more or less in accordance with Dr. Carpenter’s 
plan ; but the Family Nummulitince is made more than usually comprehensive, and 
the genera are associated in the following manner : — (a.) Tnvolutina, Archcediscus, and 
Spirillina — (b.) Pullenia, Sphceroidina, ? Rupertia, Endothyra, Cribrospira, Bradyina, 
and Amphistegina — (c.) Nonionina, Polystomella, Cyclammma, Operculina, and 
Nummulites — (d.) Fusulina, Schivagerina, and Hemifusulina — (e.) Heterostegina, 
Cycloclypeus, and Orbitoides. There are elements of interest in such a grouping; though, 
in common with the rest of the scheme, it is based more on the general form of the test 
than on its minute structure, the existence of intermediate varieties, or other indications 
of genetic relationship. 
The foregoing historical sketch has not been drawn up in order to discredit or in any 
way to depreciate the labours of which it is a brief and imperfect record, but because at 
every stage something is evolved that the systematist must take into account. Observers 
approaching the subject from various points have formed different estimates of the relative 
importance of the characters available for purposes of classification : and the modifications 
proposed in each successive scheme have been dictated by acknowledged defects in 
those previously existing. 
The study of the Foraminifera as assemblages of forms grouped round a compara- 
tively small number of central or typical species, as advocated by Carpenter and his 
colleagues, is, I am convinced, the only means of arriving at a correct understanding of 
the biological relations of the group ; but this mode of treatment, whilst determining the 
general lines of classification, furnishes no direct basis for the construction of a synopsis 
suited to the requirements of the systematic zoologist. The scheme which I now venture 
to propose differs in many respects somewhat widely from that foreshadowed by the authors 
referred to, but in its essential elements there is little or nothing that is incompatible with 
the conclusions they have so ably expounded ; and I have the satisfaction of knowing that 
it has their general approval. Every attempt to arrange in single series a class of organisms 
of which the constituent groups are apt to run in parallel lines, or even sometimes to 
form, morphologically speaking, independent circlets, is of necessity open to objection at 
