WHAT IS EOZOON ? 85 



another by nothing else than the proper walls of the chambers, 

 — which, as I shall presently show, are traversed by multi- 

 tudes of minute tubuli giving passage to pseudopodia, — the 

 coalescence of these pseudopodia on the external surface would 

 suffice to lay the foundation of a new layer of sarcodic seg- 

 ments. But where an intermediate or supplemental skeleton, 

 consisting of a thick layer of solid calcareous shell, has been 

 deposited between two successive layers, it is obvious that 

 the animal body contained in the lower layer of chambers 

 must be completely cut off from that which occupies the 

 upper, unless some special provision exist for their mutual 

 communication. Such a provision I believe to have been 

 made by the extension of bands of sarcode, through canals left 

 in the intermediate skeleton, from the lower to the upper tier 

 of chambers. For in such sections as happen to have tra- 

 versed thick deposits of the intermediate skeleton, there are 

 generally found passages distinguished from those of the 

 ordinary canal-system by their broad flat form, their great 

 transverse diameter, and their non-ramification. One of these 

 passages I have distinctly traced to a chamber, with the cavity 

 of which it communicated through two or three apertures in 

 its proper wall; and I think it likely that I should have been 

 able to trace it at its other extremity into a chamber of the 

 superjacent tier, had not the plane of the section passed out of 

 its course. Eiband-like casts of these passages are often to 

 be seen in decalcified specimens, traversing the void spaces 

 left by the removal of the thickest layers of the intermediate 

 skeleton. 



" But the organization of a new layer seems to have not un- 

 f requently taken place in a much more considerable extension 

 of the sarcode-body of the pre-formed layer; which either 

 folded back its margin over the surface already consolidated, 

 in a manner somewhat like that in which the mantle of a 

 Cyproea doubles back to deposit the final surface-layer of its 

 shell, or sent upwards wall-like lamellae, sometimes of very 

 Hmited extent, but not unfrequently of considerable length, 

 which, after traversing the substance of the shell, like trap- 

 dykes in a bed of sandstone, spread themselves out over its 



