736 
DE. W. B. CAEPENTEE AND ME. H. B. BEADY ON 
mate layer and the exterior, it might be thought not improbable that these interspaces 
were tilled with water from without, and constituted a kind of aquiferous system. But 
since it may be certainly affirmed that no such passages existed, and that the interspaces 
had no other communication with the exterior than through the systems of radial 
tubes connecting the labyrinthic systems of successive lamellae, which must certainly 
have been occupied by the sarcode-body of the animal, there was no provision for the 
admission of water to the interspaces, or, if it did enter to replace the sarcode on its 
withdrawal from them, it must have remained stagnant in these recesses. If, on the 
other hand, the interspaces remained full of sarcode through the whole life of the 
organism, there is no difficulty in comprehending that, though cut off from direct com- 
munication with the exterior, the sarcodic segments of the interspaces would share in 
the vital activity of the entire composite mass. Knowing what we do of the semifluid 
condition of living protoplasm, and of the interchange which is incessantly taking place 
between the component particles of the segments, however numerous and segregated 
they may be, into which the sarcodic body of one of these aggregate organisms is divided, 
there is not the least difficulty in understanding how nutritive material might have been 
conveyed through the radial system into the innermost penetralia of the sphere of Par- 
ekria, notwithstanding their investment by any number of concentric layers, however 
thick*. 
Explanation op the Plates of Parkeria. 
PLATE LXXII. 
Ideal representation of the internal structure of Parkeria ; the different parts shown 
in Plates LXXIII. and LXXIV. (from actual specimens) being here combined so as 
to show the relations of those parts to each other. In the upper transverse section, 
of which the plane passes through the centre of the sphere, the general arrangement of 
the concentric layers around the primordial chamber-cone is displayed ; and the inter- 
ruption of the ordinary alternation of solid lamellae and interspaces crossed by radial 
processes, by the interposition of the four thick layers IH\ l 2 l 2 , l 3 l 3 , and IH 4 , is shown. 
The details of the structure of the layers immediately surrounding the chambered cone 
are represented on a larger scale in Plate LXXIII. figs. 1, 2 ; and the details of the struc- 
ture of the thick layers are shown in Plate LXXIV. fig. 5. — In the vertical planes, a 
* In my Memoir on Orbitolites (Philosophical Transactions, 1 856, §§ 12, 34) I showed that the entire disk, 
however numerous may he the concentric zones of which it is formed, is occupied during life by the sarcodic 
body of the animal, which continues to fill even the primordial chamber ; notwithstanding that this chamber 
and the zones that surround it are in but very indirect relation with the exterior, through the pores of the 
peripheral zone. And since the above was written, I have obtained from the Deep-Sea Dredgings of the Por- 
cupine Expedition (1869) a complete confirmation of the view taken in the text. For on examining the internal 
structure of the largest nautiloid Lituolce, I find extensions from each chamber-cavity prolonged into its thick 
arenaceous wall ; which thus presents, though in a rudimentary condition, a labyrinthic structure whose relation 
to the chamber it surrounds is essentially the same as in ParTceria. , 
