HUXLEY AND HIS WOKK. 769 



difficult to devise half a dozen very pretty vertebral theories, all equally 

 true, in the course of a summer's day." He naturally reached not only 

 "the negative conclusion that the doctrine of the vertebral composition 

 of the skull is not proven," but "the positive belief that the relation of 

 the skull to the spinal column is quite different from that of one part 

 of the vertebral column to another." 



The blow thus dealt against the Owenian archetype was a serious one, 

 and it was nearly coincident with the growing adoption of the doctrine 

 of evolution and the overthrow of the doctrine of types and patterns. 

 At any rate, the old idea of the vertebration of the skull became an 

 idea of the past. Owen continued to preach it, but his disciples 

 abandoned it, and he was soon left without a single notable follower. 



YI. — Classification of Ganoid Fishes. 



The designation of Ganoidei was originally given by Agassiz to a 

 heterogeneous group of fishes distinguished by a covering of what were 

 called ganoid scales and having no other common characters; some of 

 its representatives even lacked the " ganoid " scales. But most of the 

 extinct species, at least, were really structurally affiliated and such 

 were segregated by Johannes Miiller in a comparatively natural group 

 distinguished by cerebral, cardiac, and intestinal peculiarities, and for 

 this group was retained the Agassizian term Ganoidei. Its constituents 

 were contrasted under two subordinate groups named Chondrostei and 

 Holostei. The families of the latter group were evidently related in 

 various degrees, but such degrees were not expressed in the arrange- 

 ment of the families, and the families themselves were mostly defined 

 by superficial characters of little value. The appointment of Huxley 

 to the professorship of natural history in the Government School of 

 Mines led him to investigations which culminated in a " Preliminary 

 Essay upon the Systematic Arrangement of the Fishes of the Devonian 

 Epoch" (1861), and "Illustrations of the structure of the Crosstopery- 

 gian Ganoids" (1806). He jiroceeded "to reconsider the whole question 

 of the classification of the fishes of this epoch, and, eventually, to arrive 

 at results which seem to necessitate an important modification of the 

 received arrangement of the great order of Ganoidei." He recombined 

 the Chondrostei and Holostei, and then distributed the aggregate 

 (which he designated as an order) into five suborders in the following 

 manner : 



Ordo GANOIDEI. 1 

 Subordo I. — Amiable. 

 Subordo II. — Lepidosteid^;. 



Subordo HI. — CltOSSOPTERYGIDiE. 



Fain. 1. — Polypterini. 



Dorsal lin very long, ranltifid ; scales rhomboidal. 

 Polypterus. 



1 Memoirs of the Geological Survey of the United Kingdom. Figures and descrip- 

 tions illustrative of British Organic Remains, Decade X, pages 23, 24. 



SM 95 19 



