734 
DE. W. B. CAEPENTEE AND MB. H. B. BEADY ON 
the labyrinthic substance of the lamella come to equal that of the interspaces, but its 
peripheral extensions exhibit increased regularity, and become the ‘radial processes’ 
already described as characteristic components of the subsequently-formed layers. 
18. Passing now to the outer or last-formed portion of the sphere, we find it to con- 
sist of a solid layer of cancellated substance, resembling the solid layers (l\ l 2 , l 3 , Plate 
LXXII.) by which we have seen the regular growth to have been previously interrupted, 
but of greater thickness and coarser texture (Plate LXXIY. fig. 5). Its inner surface 
is bounded, like that of the ordinary lamellae, by a continuous floor (Jl, jl , Jl) which 
cuts off its chamberlets from the neighbouring interspaces (int, int) ; but its labyrinthic 
system is connected with that of the lamella it encloses by the radial tubes (t, t); and these 
seem to extend through nearly the whole thickness of the layer, each being the centre, 
as shown in Plate LXXY. fig. 4, of a group of chamberlets disposed around it (like the 
cells clustered round the vascular canals in an ossifying cartilage), with all of which it is 
probably in direct or mediate communication. If each of these tubes (as appears pro- 
bable) served as a centre of growth, conveying a stolon-process of sarcode from the sub- 
jacent lamella, it maybe readily conceived that the group of chamberlets which surrounds 
it would project from the general surface, at any rate during the period of most rapid 
increase ; and that thus would be produced the tuberculated aspect, by which, as already 
stated (§ 6), the specimens that seem best to represent the original condition of the 
organism are characterized. It may be considered not improbable, however, that the 
intervening depressions were subsequently filled up by the growth of the cancellated 
substance, so as to constitute one uniform surface. 
19. The strongly marked dissimilarity between the fabric of Parkeria as now described, 
and that of any Foraminifera previously known, whether recent or fossil, renders it im- 
possible to predicate with certainty what was the precise relation of the sarcode-body of 
the animal to its Arenaceous ‘ test.’ Looking to the manner in which the earliest cancel- 
lated lamellae are attached to the surface of the original chambered cone, it cannot, I 
think, be doubted that the sarcode which occupied the latter spread over its exterior, as 
in Foraminifera generally'*; and that it was by this layer of sarcode that the walls of 
the first labyrinthic structure were built up. The mode in which each subsequent can- 
cellated lamella was formed, however, not in immediate superposition on that which 
preceded it, but separated from it by a considerable interspace, and only connected with 
it by the ‘ radial tubes,’ is not so easily conceived. That each of these tubes contained a 
‘ stolon-process’ from the sarcodic substance of the previous lamella, may be considered 
next to certain. And the manner in which the chamberlets of the succeeding lamella 
are grouped around the extremities of the ‘ radial tubes,’ seems to indicate that the ex- 
tensions of these sarcodic ‘stolon-processes’ furnished the instrumentality by which the 
materials were collected and arranged for rearing the walls of those chamberlets. It is 
difficult, however, to conceive (1) how the solid floor was laid, upon which those walls 
were built up (§ 13), if this floor was entirely destitute of support from beneath ; and (2) 
* { Introduction to the Study of the Foraminifera §§ 33-36. 
