220 THE VOYAGE OF H.M.S. CHALLENGER. 



1834, Meyen made the first communication upon two Rhizopoda belonging to this group, 

 Physematium and Sphcerozoum, for which he constituted a special class of Infusoria 

 (Palmellaria). In 1838,Ehrenberg described some fossil siliceous species, under the name 

 Polycystina, and made the discovery eight years later (in 1846) that masses of rock 

 in the island of Barbados contained a very large number (more than 300 species) of 

 similar delicately perforated flinty skeletons. Ehrenberg subsequently discovered a great 

 number of other skeletons belonging to this group, some of these being fossil in Tertiary for- 

 mations, and others being found in deep-sea soundings. He concluded, wrongly, that these 

 were the shells of highly organised animals related to the Polyzoa and Echinodermata. 



" The first accurate observations and correct views upon living Radiolarian organisms 

 we owe to Professor Huxley, 1 who, in 1851, carefully described several species, under 

 the name ITialassicolla. Those examined by him in a living condition were partly 

 solitary forms (really belonging to the present genus Thalassicolla), partly social 

 forms (of the genera Collozoum, Sphcerozoum, Collosphcera, Siphonosphcera). These 

 Huxley recognised as Protozoa, from their being equivalent to single cells, and 

 rightly described their central nuclei, also the vacuoles in the surrounding jelly, the 

 yellow cells, &c. 



" A far greater number of living species was soon after described by Johannes Miiller 

 of Berlin, who had observed them alive, during a period of ten years, especially in the 

 Mediterranean. He observed, for the first time, the pseudopodia forming an anastomosing 

 network, and radiating outwards from the unicellular body, and the flowing of the granules 

 along them. This movement he compared, rightly, with that in the Foraminifera. His 

 numerous and important discoveries he collected, shortly before his death, in his 

 classic treatise, which appeared in 1858. 2 All these various forms, the discoveries for the 

 most part of himself, were united by Joh. Miiller under the name Eadiolaria, and, as 

 siliceous Rhizopoda radiaria, placed in opposition to the calcareous Rhizopoda poly- 

 thalamia. 



" The knowledge of the Radiolaria acquired by Joh. Miiller was greatly extended by 

 one of his pupils, Professor Ernst Haeckel of Jena, who published, in 1862, an exhaustive 

 monograph of this group. 3 He first distinguished, as two principal constituents of the 

 Radiolarian organism, the inner central capsule and the outer extracapsular sarcode with 

 the pseudopodia. He gave the comparative morphology of the skeleton. In his 

 classification fifteen families, containing 113 genera, were distinguished. 



" The reproduction of the Radiolaria by means of swarmspores, which arise in the 

 central capsule, was first clearly observed by Cienkowski in 1871. 4 He first propounded 



1 Ann. and Mag. Nat. Hist., ser. 2, vol viii. pp. 433-442, 1851. 



3 Ueber die Thalassicollen, Polycystinen und Acanthometren des Mittelmeeres, Abhandl. d. k .Akad. d. Wiss. Berlin, 

 pp. 1-62, 1858. 



3 Monographie der Radiolarien, Berlin, 1862. 



4 Ueber Schwarmerbildung bei Radiolarien, Archivf. mikrosk. Anat., vol. vii. pp. 372-381, 1871. 



