108 



Occasionally these calcareous appendages are so large as to consti- 

 tute distinct pillars passing completely across the cell (2, g). 



The peculiar points which distinguish the structure of this organ- 

 ism from that of any recent Foraminifera hitherto described, are the 

 existence of the visible laminae in the parietes of the shell (arranged 

 at right angles to the direction assumed by the pseudopodian tubes), 

 and the calcareous columns and small papillae seen in the interior of 

 each cell. The question to be next solved is, how have these pecu- 

 liar features originated ? At first I was disposed to believe that, after 

 the segment had formed its calcareous covering, it possessed the power 

 of thickening its walls by the deposition of concentric layers of cal- 

 careous matter to every part of its inner surface. Several difficulties, 

 however, rendered this explanation unsatisfactory. First, the direc- 

 tion assumed by the lamellae, as seen in the two sections, did not 

 bear a sufficient relationship to the internal contour of each cell. 

 Secondly, it was only legitimate to assume that if such successive 

 internal growths had taken place, they would have occurred consen- 

 taneously throughout the entire organism ; in which case the number 

 of laminae would have increased as we approached the centre of the 

 organism. The result of this would have been, that the laminae 

 required to produce the thickness of the cell-wall, as seen at 2, c, 

 would have entirely blocked up the innermost cells of the animal. 

 This, however, has not been done : the relative size of the cells and 

 the thickness of their walls, as seen in the innermost and smallest 

 convolutions, appear to be proportionate to the relative dimensions 

 of the analogous parts in the more external and larger spirals. 



A third difficulty arose from the arrangement of the pseudopodian 

 tubes at the margins of the convolutions, as seen at 2, a, c and c. At 

 2, a, we observe that the divergence of these tubes, which radiate from 

 the interior of the cell in opposite directions, produces in the vertical 

 section a small, triangular, translucent spot, of which the apex is 

 directed towards the centre of the animal. In this translucent tri- 

 angle the lines of growth are distinctly visible. At the opposite side 

 of the specimen (2, c), which forms an older portion of the organism, 

 we find that the increase in the thickness of the parietes of the cell 

 has also led to a corresponding increase in the size of this triangular 

 spot ; but the enlargement is obviously at its base, or external por- 

 tion, its internal apex being unchanged. The tubes, retaining their 

 primitive direction, continue, of course, to diverge more and more as 

 each addition of new layers produces their elongation, which would 



