OF THE RIIIZOPODA IN GENERAL :—RETICULARlA. 31 



than those which communicate with tlie adjacent chambers, and the last-formed chambers 

 having only a single orifice* of communication with the exterior, from which alone pseudopodia 

 are put forth (PL III, fig. 3). But all these openings are usually so free, that no obstacle can 

 exist to a transmission of nutrient materials obtained by the pseudopodia put forth on the 

 exterior, to the segments of sarcode-body that are furthest removed by it, by a circulation of 

 granules through the entire mass analogous to that which has just been described ; and thus 

 the physiological condition of the animal of Miliola and its allies may be considered to be in 

 all essential respects the same as it is in Gromia. This will still be the case, even when the 

 number of such segments is immensely multiplied by the subdivision of the principal sections, 

 as in the animal of Orbitolites (PI. IV, fig. 14), Orbiculina, and Alveolina ; and the evidence 

 which the author has been fortunate enough to obtain in regard to the first of these types is 

 sufficient to show that there is no indication of deficient vitality in the portion of the sarcode 

 body which occupies the centre of the largest disk, the character of its substance being 

 precisely the same throughout. 



36. A very different condition presents itself, however, with the two great groups 

 (together constituting by far the largest proportion of the entire series), of whicii Rotalia and 

 Operculina may be regarded as the types. For in these tiie apertures in the septal planes by 

 which the chambers communicate with each other, and by which the special communication 

 is established between the last chamber and the exterior, are so much narrowed that they 

 are sometimes not easy to be discovered ; but, on the other hand, the lateral walls of the 

 chambers are everywhere perforated, more or less closely, with pores for the exit of pseudo- 

 podia. Hence when a living Rotalia is under observation, its pseudopodia are seen to extend 

 themselves from every part of its surface (Plate III, fig. 1), and not to proceed only from the 

 orifice of the last chamber, as in IlUiola. When the pseudopodia have been entirely retracted, 

 however, it is generally observable that those first put forth proceed from the orifice (or 

 orifices) of the septal plane of the last chamber; and frequently a considerable time elapses 

 before the pores of the lateral walls give exit to protoplasmic filaments. , Often, again, these 

 filaments are put forth only from the two or three last-formed chambers. Still, when such an 

 animal has remained long undisturbed, its pseudopodia may be seen to extend themselves 

 from all the pores on its surface. If these are used for the introduction of alimentary 

 materials into the body, it is obvious that such materials only can thus enter, as are in a state 

 of sufficiently fine division to pass through these pores. No difficulty need be felt on this score 

 in the case of the Rotaline group, in which the diameter of the pores, being commonly as 

 much as 1 -3000th of an inch, allows the passage of pseudopodia of by no means the smallest 



of sufficient importance to differentiate groups which are so intimately allied in their general physiological 

 conditions, especially when it is borne in mind that some of the Milolida form their shells, after the 

 manner of Difflugia, by the agglomeration of particles derived from without, instead of by an e.xudation 

 from within. Moreover, if Gromia be regarded as the monothalamous type of the Milioline series, it 

 naturally fills a place exactly parallel in rank to that of OrbuUna in the Rotaline. 



* The single large mouth is sometimes replaced, as in Peneroplis and Orbitolites, by a series of 

 pores ; but these, being limited to the " septal plane," have no relation whatever to those which allow 

 the passage of pseudopodia through the lateral walls of the chambers of Rotalia and Oiierculina. 



