REPORT ON THE RADIOLARIA. 1639 



very large, usually twice to three times as broad as the inner shell, and irregularly 

 polygonal; the usual and prevailing form is pentagonal, but hexagonal meshes are also 

 often intermingled, more rarely meshes with four, seven, or eight sides. 



The cylindrical tangential tubes possess in general the same shape as in the similar 

 Aulosphserida, have a thin wall, are filled by jelly, and contain a delicate axial filament 

 in their axis ; they differ, however, in a peculiar constant character ; in the middle of 

 each tube is inserted an inner radial beam coming from the inner shell, so that both 

 together have the form of a T. The central point of insertion has a somewhat shorter 

 radial distance from the centre of the body than the two nodal points on both ends of 

 the tangential tube, so that the latter is slightly geniculate (figs. 15). The two 

 halves of each tangential tube are usually somewhat thinner on the central end (where 

 the inner radial beam is inserted), thicker on the distal end (where the outer radial 

 tube arises) ; at both ends they are closed by a thin transverse septum. Often also 

 some other septa are developed, so that each tangential tube seems to be composed 

 of four to six joints or segments. Usually the tangential tubes are armed with spines 

 or anchor-threads, similar to those of the inner radial beams. The length of the single 

 tangential tubes is usually between O'l and 0'3, their diameter from O'Ol to 0'02. 



The nodal points of the outer lattice-sphere, in which the outer radial spines arise, 

 seem to possess the same structure as in the similar Aulosphserida. Since three 

 tangential tubes are connected in each nodal point, in its centre is the union of three 

 small astral septa or sutural partitions. The small nodal cavity on the inaide of the 

 nodal point has probably three small pores, which lead into the three tangential tubes 

 between the three astral septa. A fourth pore probably leads from the nodal cavity 

 into the cavity of the hollow radial tube. This structure is difficult to observe, but 

 seems to be demonstrated by the fact, that in the complete and carefully purified skeletons 

 which are treated with hot mineral acids and afterwards dried, all cylinders, the 

 tangential as well as the radial tubes, become easily filled by air (compare the descrip- 

 tion of the similar structure in the Aulosphserida). 



The external radial tubes which arise in the nodal points of the outer shell are either 

 cylindrical or cylindro-conical, straight, and usually about as long as the diameter of the 

 inner shell. Their structure and armature is the same as in the similar Aulosphserida. 

 In the axis of each radial tube runs a delicate axial filament, which is connected with 

 its thin and fragile wall either by filiform transverse branches or by delicate transverse 

 septa. The outside of the radial tubes is either smooth (figs. 3-5) or armed with 

 scattered spines (fig. 4) or with verticils of lateral branches ; each verticil is usually 

 composed of three or four branches. The distal end of the radial tubes is rarely simple, 

 pointed ; it is usually armed with a spathilla of three or four curved terminal branches 

 (figs. 3, 5) sometimes with an elegant corona composed of twenty to thirty thin radially 

 divergent branches (fig. 4). 



