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



hypothetical genealogical tree, which I then published, has been stiU further carried out 

 in Chapter VI. of the present Introduction (see §§ 153-200). 



253. General Survey of the Growth of our Systematic Acquaintance with the 

 Radiolaria from 1834 to 1885. 



1834. Meyen (L. N. 1) describes 2 genera and species of Q oWo A &\\Q,:—-Sphwr ozoum fuscum 



and Physematium atlanticum. 

 1838. EiiRENBERG (L. N. 2) founds the family Folycystina upon 3 fossil genera (with 6 species): — 



Lithocampe, Cor7iutdla, Haliomma. 

 1847. Ehrenbeeg (L. N. 4) publishes his preliminary communications regarding the fossil Polycystina 



of Barbados and distinguishes 282 species, distributed in 44 genera and 7 families. 



In the tabular view of the genera he distinguishes two orders:— I. So lit aria — 



(1) Halicalyptrina, (2) Lithochytrina, (3) Eucyrtidina ; and II. Composita — 



(4) Spyridina, (5) Calodictya, (6) Haliommatina, (7) Lithocyclidina (compare L. N. 16 



pp. 214-219). 

 1851. Huxley (L. N. 5) gives the first accurate account of living Eadiolaria, and describes 2 



species of the genus ThalassicoUa (miclcata and punctata) ; under the latter are included 



4 genera of Sphferozoea: — Collozoum, Sphwrozoum, CoUosphwra, Siphonosphcera 



(compare L. N. 16, pp. 12-14). 



1854. Ehrenberg (L. N. 6) publishes in his Mikrogeologie, figures of seventy-two species of fossil 



Polycystina (without descriptions). 



1855. Johannes Muller (L. N. 8, p. 248) describes the first Acantlwmctra, and elucidates its 



affinity to Huxley's ThalassicoUa and Ehrenberg's Polycystina. 



1858. Johannes Muller (L. N. 12) establishes the new group Eadiolaria as a special order of the 

 Ehizopoda, and includes in it the ThalassicoUa, Polycystina, and Aeanthometra as closely 

 related families. He opposes these radiate Pihizopoda to the Polythalamia, and 

 describes 50 species observed by him living in the Mediterranean, these he arranges in 

 20 genera, of which 10 are new. The figures are contained in eleven plates (see L. N. 16, 

 pp. 22-24). 



1858. Clapaeede (L. N. 14) describes the first Plectoidean {Plagiacantha arachnoides) and 

 two species of Acanthovietra, which he had observed living in Norway (see L. N. 16, 

 p. 18). 



18.60. Ehrenberg (L. N. 4) gives a short diagnosis of 22 new genera of Polycystina, based on 

 the investigation of numerous deep-sea species brought up by Brooke from the depths 

 of the Pacific Ocean. The number of his genera is thus increased to 66 (compare 

 L. N. 16, pp. 10, 11). 



1862. Ernst Haeckel (L. N. 16) embraces in his Monograph of the Eadiolaria all the species 

 hitherto known either by figures or descriptions, and arranges them in 15 families and 

 113 genera ; of which latter 46 are new. The number of new species observed hving 

 amounts to 144. In a " survey of the Eadiolarian fauna of Messina " (p. 565) he 

 records 72 genera and 169 species. Most of these are figured in the accompanying 

 atlas of thirty-five plates. 



