28 
DE. CAEPENTEE’S EESEAECHES ON THE EOEAIVUNIPEEA. 
the interseptal passages branch off from these two spiral canals, is well seen in fig. 1, 
Plate VI., and also in fig. 10, Plate IV.; and this arrangement is shown in fig. 6, 
Plate IV. to extend to the septa between the chambers of the innennost convolution. 
The relations of the different parts of the system are brought extremely well mto view 
in fig. 12, Plate IV., which represents a tangential section of a young shell, the rapid 
curve of 4hose spire causes the planes of even the contiguous septa to vary greatly in 
their direction. The spiral canals, though only running along the angles of the mar- 
ginal cord, pretty obviously communicate with the plexus of passages which it contams; 
and thus the interseptal system of one whorl is brought into direct connexion with that 
of the preceding. It is to be remembered, however, that independently of such con- 
nexion, the spiral mode of growth of itself brings about a continuity of the canal-system 
throughout, by means of the marginal plexus; the consecutive whorls not being added 
one to another like the successive annuli of Cycloclypeus, each of which is (so^ to 
speak) closed or complete in itself; but being formed by the prolongation of the spual 
lamina and of the marginal cord, which may be considered as always ojyen to mdefinite 
extension. i • x 
160. In regard to the uses of this canal-system, I have not at present anything to add 
to what I have already stated when describing its distribution in Cycloclypeus (•![ 107) ; 
I shall have the opportunity, however, of discussing them more fully m a subsequent 
Memoir upon forms in which this system is still more remarkably developed. 
161. I have attempted to determine by a re-examination of my preparations oiNum- 
mulites, with the additional light afforded by the structure of Operculma, whether an 
arrangement of the canal-system prevails in the former at all comparable to that which 
I have shown to exist in the latter. In those which have undergone the ordinary 
fossilizing process, it is difficult to discover more than vague indications of its existence. 
But the peculiar process of silicification of Foraminifera, to which attention has been 
recently drawn by Professor Eheenbeeg*, has afforded an unexpected verification of the 
anticipations which the similarity of these two genera in other points of structui’e had 
led me to form as to this. For by the infiltration of silex tinged with silicate of uon 
into the cavities of Foraminifera, whilst their calcareous shells have undergone decom- 
position and removal, a most perfect series of casts are presented, not merely of the 
chambers, but of the canal-system where this exists. And in his figme of such a cast 
ofNummuUtes striata (taf. 5. fig. 2), Professor Eheenbeeg has given a most beautiful 
representation of the canal-system of the marginal cord, and of its communications with 
the interseptal canals, so closely corresponding with that which, long before the publica- 
tion of his memoir, I had worked out in Operculina, that no doubt can fairly remain 
as to the essential similarity between these two types in this important feature of then- 
organization f. 
* liber den Griinsand und seine Erlauterung des organischen Lebens. Aus den Abbaldlungen der 
Konigl. Akademie der Wissenscbaften zn Berlin, 1855. 
t I may here remark upon tbe confirmation afforded by other parts of this most valuable memom to the 
results of my researches upon Orhitolites and Cycloclypeus ; the various figures given by Professor Ehbexbekg 
