170 



P. criipa has protruded minute filamentous pseudopodia. May not 

 these, in addition to their functions as organs of locomotion, also 

 have the power of absorbing a supply of nutritive fluid ? Dr. Car- 

 penter states, " that in the Actinia fluid seems to enter and to be 

 ejected, not only through the mouth, but through the tentacula also ;" 

 — (* Principles of General and Comparative Physiology,' p. 117). If 

 this be done by one of the more highly organized polypes, it is not 

 improbable that, amongst the Foraminifera, the pseudopodia — which 

 appear to take the place of the tentacula in the higher class of organ- 

 isms — may also assume this function of absorption. The lower we 

 descend in the animal scale, the more do we find the objects nourished 

 by this process of exosmose and endosmose. 



It is probable that the innermost convolutions may have the power 

 of protruding pseudopodia, as well as the external ones ; for though the 

 calcareous portion of each of the latter completely embraces and en- 

 closes the former, the soft animal, as will be seen on referring to fig. 6, 

 does not so completely cover in its own smaller whorls. But whilst in 

 the decalcified animal we have a sort of umbilical cavity, in the calca- 

 reous shell this depression is filled up by a solid mass of carbonate of 

 lime, into which the decalcified animal does not extend, but which 

 nevertheless is apparently thickened by each additional convolution 

 added on the growth of the shell ; so that what in the one is the 

 thinnest, in the other becomes actually the thickest part of the or- 

 ganism. But, as if to compensate for this, the surface of this central 

 ■calcareous nucleus is pitted by small but deep depressions, which 

 may be designed to facilitate the exit of pseudopodia from the inner- 

 most convolutions. This peculiar structure probably explains Ehren- 

 berg's observations on his Cuxhaven specimens, when he found that 

 the filaments were projected from the umbilical region in bundles, and 

 he suggests that there may exist at that point distinct and larger 

 apertures. Tt is however more probable, since no such large apertures 

 are visible, that this aggregation of the pseudopodia into bundles, at 

 the umbilical region, may have been occasioned by these depressions 

 in the calcareous substance. Similar depressions exist in the little 

 species which I suppose to be analogous to his Geoponus stella-bo- 

 realis. 



Another curious question arises out of this latter point. Since the 

 external convolutions of the soft animal do not extend into this calca- 

 reous nucleus which covers up the central cells, — and yet each addi- 

 tional convolution contributes externally to its thickness, — from what 

 part of the organism are these calcareous additions to the central por- 



