REPORT ON THE RADIOLARIA. 55 



differences in tlae size, form, or distauce of the meslies or j^ores). In both groups the jDores 

 ma}^ be either anguhir or round ; so that there may exist altogether four different main 

 forms of network — (A) reguhir hittice with equal hexagonal pores ; (B) regular lattice with 

 etpal circular pores ; (C) irregular lattice with unequal polygonal pores ; (D) irregular lattice 

 with unequal roundish pores. Besides these modifications, the p>ores may be prolonged 

 into tubules which are directed radially towards the outside (rarely towards the inside) of 

 the sphere. In other cases they are surrounded by elevated or honeycomb-like frames. 



The Radial Spines exhibit in the Sphseroidea the greatest variety in form, size, 

 disposition, &c., and their numerous modifications serve mainly for the distinction of 

 genera, their peculiar formation and size also for the distinction of species. In general 

 we may distinguish as the most important modifications primary and secondary spines. 

 The primary spines or " main spines " are commonly direct outward prolongations of the 

 internal radial beams, connecting the concentric shells. The secondary or " by-spines " 

 arise only from the surface of the lattice-shell, without reference to the internal beams. 

 The by-spines are commonly smaller, and much more numerous than the main spines. 

 Eegarding the form, the radial spines are either roundish (cylindrical or conical, often 

 also club-shaped, rarely spindle-shaped) or angular (commonly three-sided, prismatic or 

 pyramidal). The spines are constantly solid, never hollow ; the " internal canals," 

 described by some authors, are only microscopic views of the transparent edges. In 

 many cases the spines are branched or forked. The most important difference in the 

 variable shape of the sj)ines is their regular or irregular number and disposition, which 

 " afford characters for the distinction of our five families. 



The Three Dimensive Axes — or the three diameters of the sphere, perpendicular 

 one to another — are in the great majority of the Sphseroidea significant in the 

 promorphological consideration of the body, and are indicated either by the position of 

 the external radial spines, or at least of the internal radial beams, connecting the concentric 

 spheres. Commonly two radial spines are placed opposite in each axis. The most 

 perfect group in this respect seems to be that of the Cubosphserida, in which the three 

 axes are represented by three pairs of spines. Next come the Staurosphserida, in which 

 two axes in cross-form are exhibited by two pairs of spines. The most simple group are 

 the Stylosphserida, in which only one j^air of spines is developed, indicating one single axis. 

 These three families form together a continuous natural series, — the Sphseroidea 

 \yith. real dimensive axes, — and exhibit at the same time relations to the three 

 other suborders of Sph se r e 11 ar i a, the Larcoidea, Discoidea, and Bru- 

 no i d e a respectively. At both ends of this series stand two other families, on one 

 side the Liosphserida, without any radial spines on the surface of the sphere, on the 

 other side the Astrosphserida, in which the radial spines are developed in great and 

 variable numbers, at least eight to twelve, commonly twenty to forty, often more than 

 a hundred or even a thousand. 



