174 



presence in other genera is obtained from the occurrence of foreign 

 bodies within their articulations, and which have not been satisfacto- 

 rily seen in the subject of this memoir. Hence the existence of the 

 internal digestive cavity at all is rather admitted, from the general 

 analogy which the Polystomella bears to other forms in which I have 

 proved its presence. We find indeed little more than an animated 

 slime, which, when dried, shrinks away — like some of the Acephalce — 

 to almost nothing ; sometimes scarcely staining the glass upon which 

 it is attempted to be preserved. Neither can this species be satisfac- 

 torily classed with any of the less complex forms of Polypi/era ; for 

 even the " Sertulariens " of Milne-Edwards, the simplest groups 

 of his " Polypes Anthozoares" are described as " ayant un ouverture 

 servant en meme temps de bouche et d'anus : " and this is surrounded 

 by a ring of tentacula. All these characters, which are also commonly 

 recognized by other zoologists, are incompatible with the simple or- 

 ganization of the soft animal of the Polystomella crispa. It is per- 

 fectly true that in Peneroplis, and many other allied genera, we find 

 numerous apertures, which, for want of a better name, are termed 

 " oral," but these exhibit little affinity to the single central mouth and 

 encircling tentacula of the true polypes. The orifices in the calca- 

 reous shell of the Foraminifera are probably move analogous to the 

 minute tubular openings in some of the Porifera ; and though often 

 numerous in one individual, there is no possibility of dividing them 

 into two groups, assigning to the one the special functions of a mouth, 

 and to the other that of an excretory outlet. 



The rapid extension of physiological investigations shows, with in- 

 creasing clearness, the impossibility of producing any satisfactory 

 linear arrangement of organized structures ; and in the objects under 

 consideration this difficulty is especially manifest. In the low organi- 

 zation of their gelatinous tissues, we are reminded of the slimy forms 

 of the Pmifera on the one hand and the Difflugia on the other ; only 

 the horny skeleton and the triradiate calcareous spicula of the sponge 

 are here exchanged for an external calcareous skeleton and an elastic 

 lining membrane. But the existence of a decided internal digestive 

 cavity, together with their well-defined retractile pseudopodia, give 

 the Foraminifera a claim to a higher rank than is held by any known 

 Porifera. The extension of the stomach, if such the gelatinous ca- 

 vity may be called, throughout the organism, reminds us again of the 

 Am<eb<B, as well as the simpler species of Hydraform polypes, whilst 

 many of the lower Acephala present an analogous watery gelatinous 

 structure, numerous retractile filamentous organs of locomotion, and 



