GENUS ORBITOLITES. Ill 



zone will issue from the marginal pores, and will give origin to the pseudopodia by whose 

 action the life of the entire composite organism must be sustained. The analogy of other 

 Rhizopods would lead us to suppose that it is by the introduction of alimentary particles 

 (chiefly minute forms of vegetation), through their means, into the mass of sarcode of which 

 they are extensions, that the fleshy body pervading the entire disk is nourished. For 

 although there is nothing like a digestive cavity in any part of it, or an alimentary tube 

 passing from one portion to another, still less any vascular communication between the 

 segments, yet as the sarcode forms one soft homogeneous mass everywhere continuous, the 

 body as a whole will receive the benefit of any incorporation of new matter with its substance, 

 in whatever situation this may be made. That organic particles small enough to pass 

 through the marginal pores are thus introduced into the chambers of the disk, is proved by 

 the curious fact that the residuum left after the decalcification of large and therefore aged 

 disks, whose animal contents have not been preserved, consists almost entirely of an 

 assemblage of remains of minute Diatomacca, Desmidiece, &c., which have obviously been 

 retained in the interior of their cavities after the assimilation of the nutriment they were 

 competent to afford. The sarcode-body of the animal, growing at the expense of the nutri- 

 ment thus appropriated, will gradually, it is probable, project itself through the marginal 

 orifices, not merely in filamentous pseudopodia, but in quantity sufficient to form a new zone; 

 and it is easy to understand, from the analogy of other Foraminifera, that such extensions will 

 coalesce with each other laterally, so as to form a complete annuhis around the entire 

 periphery of the dislc. This, at any rate, must be the case when a new zone is to be added to 

 the shell ; and it would seem as if this annulus then undergoes a thickening into segments by 

 the accumulation of sarcode at the points at which it receives the radiating pedicles from the 

 last zone of the sarcode-body included within the shell, whilst it becomes narrowed in the 

 intervening portions, which form the connecting bands between the segments. It may be 

 presumed to be by a calcareous exudation from the surface of this beaded ring of sarcode, 

 that the formation of the new shelly zone is accomplished ; and if the calcifying process com- 

 mence on the segments, and extend from these along the surface of their connecting stolons, 

 we can understand why the passages that are left for communication with the exterior should 

 arise from the intermediate divisions of the annular canal rather than from the segments 

 themselves. — Although the body of the animal is so far decolorized in the spirit-specimens 

 which alone have hitherto come under my observation as to present only a brownish hue, 

 yet as specimens that have been gathered fresh and have been then dried possess a reddish 

 aspect, which is due to the desiccated body they contain, it may be presumed that the 

 sarcode of the living Orbifolites has the same bright-red colour as that of Botalia and many 

 other Foraminifera. 



162. I have not met with the least indication that the sarcode is contained within any 

 prosier membrane ; and the absence of any such indication, notwithstanding the various 

 manipulations to which I have subjected its segments, may be taken, I think, as strong 

 negative evidence that it has no more existence in this animal than it has in the species ot 

 Foraminifera whicii have been so well studied by M. Dujardin and Prof. Schultze. Nor is 

 there the slightest trace of distinct organs, either in the mass of sarcode which forms the 

 "primitive mass" or in that which constitutes each one of the surrounding segments; and 



