NOTES ON RETieULAR[AN RHIZOPODA. 29 



the segments, but it appears to be the result of accident, 

 and the specimens are not otherwise complete. If this be 

 the normal condition of the test, and it may be assumed that 

 it is, it would suggest a near affinity to the genus Psammo- 

 spheera. That the comparatively thick and well-cemented 

 test of Psammosphcera affords free passage for the sarcode in 

 the form of pseudopodia, without any general aperture, is a 

 well-ascertained fact, and there can be no difficulty, therefore, 

 in supposing that Sorosphisra with its thinner shell of open 

 granular texture does the same ; in point of fact, these two 

 genera are in very similar position to some of the hyaline 

 calcareous Foraminifera, such as Orhulina, which depend on 

 minute foramina rather than on a large central orifice for 

 the means of extending their sarcode beyond the limits of 

 the chamber- cavities. I have long been convinced that the 

 use of the Avords " Perforate '* and " Imperforate," as a class 

 distinction amongst the Foraminifera, is an untenable one, 

 and these types are sufficient evidence that the arenaceous 

 forms at any rate are not necessarily imperforate. 



In some genera of Foraminifera, Cristellaria, for example, 

 specimens may be found in which the stoloniferous tubes 

 uniting the chamber-cavities are distinct from the radiate 

 orifices that have in succession served as the general aper- 

 ture ; but such case are rare and, as a rule, the general 

 aperture of the terminal chamber forms the passage connect- 

 ing it with the cavity of the segment next formed. It 

 follows, therefore, that in a polythalamous test like Soro- 

 sphara, in which there is no external general aperture, the 

 sarcode segments cannot be connected by stolons, and unless 

 the pores of the contiguous chamber-walls serve the purpose 

 of stoloniferous passages, the individual chambers must have 

 a separate rather than a corporate existence. We know, 

 however that the sarcode of perforate Foraminifera spreads 

 itself freely over the surface of the shell before extending 

 itself in pseudopodial filaments, and there can be little doubt 

 that the interstices amongst the sand-grains of the contiguous 

 chamber-walls are sufficient to afford free communication 

 between the segments. 



The absence of any general aperture may be held to 

 account for the irregular growth of the test and the want of 

 order amongst the segments, for it is clear that if the proto- 

 plasm exudes at all points of the surface, a fresh chamber 

 may be formed whenever sufficient has collected at one spot 

 to segregate itself into a mass of the requisite size. 



The specimen figured (PL IV, fig. 18) is the largest, and 

 on the whole the best, that has hitherto been found. In one 



