222 PEOCEEDINGS OF THE GEOLOGICAL SOCIETY. [Jan. 10, 



SO that instead of the uniform punctation which the internal surface 

 of the chamber-wall exhibits, we may find great diversities in the 

 disposition of their eocternal orifices, these being often congregated in 

 bands and clusters, with intervals of non-tubular shell-substance 

 between them. The same is the case in the recent Amphistegina ; 

 and the internal cast, or model of its animal, already referred to pre- 

 sents the same hind of variations in the course of the siliceous threads 

 which represent the pseudopodia, as those which are exhibited in a 

 higher degree by the " asbestiform layer " of Eozoon. For decalcified 

 specimens of this often show us fissures in the asbestiform layer, re- 

 sembling those left in the surface of a piece of velvet-pile by doubling 

 it back ; these fissures represent the non-tubular spaces of the shell- 

 wall, which are left by the convergence of the tubuli in other parts 

 into bands and tufts. A more marked degree of the same conver- 

 gence, bringing a large number of the pseudopodia that proceed from 

 each segment into one bundle, is frequently to be seen in parts in 

 which there is an unusual development of the intermediate skeleton 

 and canal-system. And here an additional peculiarity often pre- 

 sents itself, which is in such remarkable accordance with what I had 

 previously observed and recorded in the recent Poraminifera to which 

 Eozoon seems most nearly allied, that it is difficult to conceive that 

 accordance to be without a meaning. In my description of the canal- 

 system of Cdlcarina I had expressed my belief that the usual origin 

 of the canals of the intermediate skeleton is not from the cavities of 

 the chambers, but from lacunar spaces intervening between the out- 

 side of the proper walls of the chambers and the intermediate skeleton 

 by which they come to be overgrown ; and in my previous commu- 

 nication upon Eozoon (p. 63) I expressed the opinion that the same 

 was probably the case in that organism. These lacunar spaces, in 

 the living animal, would be occupied by films of sarcode formed by 

 the coalescence of the pseudopodia on the external surface of the 

 proper wall of the chambers ; and from these films would pass off 

 the sarcodic extensions which occupy the canal-sytem. Now in 

 those varieties of the asbestiform layer which exhibit a foliated or 

 penicillate arrangement of the silicified threads, the bands or tufts 

 which the surface of the asbestiform layer then presents are often 

 connected by plates of the same siliceous material, in which the stems 

 of the dendritic models of the canal-system are frequently implanted. 

 And these plates can in many instances be plainly seen to be formed 

 by the spreading-out of the material which formed the coalesced 

 bands and tufts ; just as the sarcodic layer on the surface of the 

 living shell is formed by the spreading-out of coalesced bundles of 

 the pseudopodia that have emerged from the chamber-wall*. 



I have thought it desirable to dwell thus fully upon the structure 

 of the Nummuline chamber-wall, and the parallel between the variety 

 of appearances which it presents in Eozoon and those exhibited by 



* This structure may be what has been described by Profs. King and Eowney 

 as " a double asbestiform layer." If so, its presence, instead of affording an ar- 

 gument against the Foraminiferal nature of Eozoon, supplies an unexpected 

 confirmation of that doctrine. 



