REPORT ON THE RADIOLARIA. 207 



radial spines, which are either regularly or irregularly disposed on the surface of 

 the spherical shell. The extreme variability and richness of form in this family is 

 mainly due to the different size, shape, and disposition of these radial spines. 



The simplest Astrosphaerida are the Coscinommida, with a single spherical 

 or polyhedral lattice-shell. To this ancestral group all other subfamilies can l)e 

 opposed as " Astrosphserida composita," since their skeleton is composed of two or more 

 concentric lattice-shells : two in the Haliommida, three in the Actinommida, four in 

 the Cromyommida, five or more in the Caryommida. In these four subfamilies the 

 concentric shells are all simple (not spongy) fenestrated spheres or endospherical poly- 

 hedra. In the sixth subfamily, the Spongiommida, the shell is wholly or partially composed 

 of spongy irregular wicker-work, with or without a medullary shell in the centre. 



The Number of the Radial Spines in the Astrosph^rida is extremely variable, and 

 ranges from eight to forty or more ; in many cases more than one hundred. Often 

 each nodal-point of the network develops on the shell surface one spine. Still 

 more frequently the number of the spines is less than that of the nodal-points. In all 

 concentric Astrosphserida, having two or more concentrical shells, we can distinguish 

 " primary spines," as outer prolongations of the inner radial beams connecting the shells, 

 and " secondary spines," developed only on the outer surface of the shell. Naturally 

 the former are of much greater importance than the latter. But we can also often 

 distinguish among the latter larger " main spines " and smaller " by-spines," the latter 

 commonly much more numerous than the former. 



The Disposition of the Radial Spiiies, either regular or irregular, is a subject of 

 great morphological interest, and remains to be exhausted by further observations. The 

 following cases of regular disposition have been observed by me — (A) eight spines, 

 opposite in paii-s in four axes corresponding to the four diagonal axes of a cube ; 

 (B) nine spines, regularly disposed at equal distances (?) (not opposed in pairs); (C) ten 

 spines, disposed at equal distances (?); (D) twelve spines, regularly disposed, corre- 

 sponding to the twelve corners of the regular icosahedron ; (E) fotii-teen spines, quite 

 regularly disposed (six corresponding to the three axes of a regular octahedron, eight 

 to the central points of its eight faces); (F) sixteen spines, regularly disposed (?); 

 (G) twenty spines (very common !), either disposed in the same manner (after the 

 law of Johannes Miiller) as in the Acantharia (?), or corresponding to the twenty 

 corners of the regular or pentagonal dodecahedron, or disposed in the same manner as 

 in many L a r c o i d e a (Tholonida, &c., to be described afterwards); (H) twenty-four 

 spines, regularly disj)osed (?); (I) thirty-two spines, quite regularly disposed (twenty 

 corresponding to the twenty corners of the regular dodecahedron, twelve to the central 

 points of its twelve faces); (K) forty spines, nearly regularly (or quite symmetrically?) 

 disposed. If the number of the spines amounts to more than forty, it is as a rule 

 impossible to determine their regular disposition in a satisfactory manner. 



