30 Revteics — Dr. G. J. Hindc on Fossil Radiolnria. 



mediaeval ignorance had cleared away. Thns the relatively large 

 'water-fleas' of streams and ditches, and the sand-like 'ammonites' 

 of the Adriatic, were olijects of curiosity for some, and the 

 DiatomacefB, mistaken for Infusoria, were before long carefully 

 studied, from both fresh and salt waters. So also the spicules of 

 Sponges were noticed, classified, and figured. Together with some 

 of the foregoing, in either a recent or fossil state, other minute 

 organisms, of great beauty in their delicacy and symmetry, had been 

 met with, but their real place in nature was not determined until 

 within fifty years ago. These, when alive in the sea, have a jelly- 

 like body, invested or supported by a complex but delicate and often 

 elegant framework of meshes and spicules, mostly siliceous. Johannes 

 Miiller, of Berlin, indicated their true alliance by grouping them as 

 "lihizopoda Radiaria seu Radiolaria," in 1858. 



These attractive little organisms were known to exist in the i\Iedi- 

 terranean and other seas, and to be fossil in thick strata at Barbadoes 

 and elsewhere. During the Voj'age of the "Challenger" in 1873-6, 

 they were found to constitute a large percentage of the ooze over 

 extensive oceanic areas. After long study of these organisms, 

 Dr. E. Haeckel, determining their essential characters and modifica- 

 tions, classified them, with descriptions and illustrations, in his '•'Die 

 Eadiolarien," 1862, and the "Report of the Scientific Results of the 

 Voyage of the ' Challenger ' during the j^ears 1873-76 " : Zoology, 

 vol. xviii, 3 parts (1887). 



The nuclear or medullary body, with its enclosing membrane or 

 open-worked shell, either central or at one end of the axis, is 

 enveloped with a protecting (cortical) sarcode, which extrudes 

 pseudopodia, and in many cases is strengthened and invested by 

 spicules, meshes, and radial spines, usually of silex, and of 

 manifold form and arrangement. The persistent forms are usually 

 regarded as belonging to the ' Polycistina ' of Ehrenberg and Miiller. 

 (Pol ijcistina=z many baskets; Pohjcijstina=: many bladders; used 

 sometimes indifferently.) 



In the case of those that have no shell, and those in which the 

 radial spines are not composed of hard silica, there is little or 

 nothing left in the fossil state. Otherwise numerous individuals 

 remain more or less perfect in various rocks of the Palaiozoic, 

 Mesozoic, and C?enozoic formations. They mostly present " either 

 simple or concentric latticed shells, some with relatively long radial 

 spines ; and they are similar in character to recent Radiolaria, and 

 probably referable to the same genera as the latter." 



However much modified in the individuals of different groups, 

 yet the inner or nuclear capsule and the outer capsular investment 

 (calymma) may be, their essential character is always recognizable. 

 The spicules in the naked forms of the Spuraellaria, and the hard 

 parts of the other groups, constitute subsidiary evidences of the 

 generic and specific differentiation. 



In these, as in other low forms of life. Nature is so lavish of her 

 productive power in the multiplicity and almost endless variations 

 of growth, that at first sight it seems to be impossible to find the 

 clue to the apparent entanglement of structural peculiarities in the 



