PEDIGREE OF FISHES. 



257 



well-known observations, the homologous parts of the 

 Ganoids are related either as progressive developments 

 or as reductions. Huxley has also prepared the way for 

 a correct apprehension of these relations. To be fully 

 convinced of this, detailed study is certainly requisite; 

 for in its absence it is impossible to imagine, how in the 

 Elasmobranchii the true branchial apparatus is wanting, 

 and how the cartilaginous arch, which, in them, replaces 

 the gills, is applied in the Ganoids, partly as the palate, 

 and partly as the attachment for the true lower jaw, while 

 the internal gills of the former, become the external gills 

 of the latter; how in the skeleton of the anterior ex- 

 tremities, a gradual simplification may be exhibited, step 

 by step, from the sharks and rays to the Ganoids, and 

 especially the sturgeon, — a process of which the two ex- 

 tremes are reached in the Teleostei on the one side and 

 the higher Vertebrata on the other — in the latter in the 

 multiform perfection of the arm and hand. 



Of the Ganoids only scattered remnants survive, the 

 sturgeon family and some few American and African 

 genera, of which, as Riitimeyer says, a flight into fresh 

 water has been the salvation. They just suffice to ex- 

 plain the relation of this once extraordinarily extensive 

 group, to the Elasmobranchii as well as the Teleostei. 



In the Teleostei, the metamorphosis of the organ- 

 ization of the Elasmobranchii initiated in the Ganoids, 

 is carried yet further. It is only with great qualifica- 

 tion that they can be termed " more highly developed," 

 in the skeleton perhaps, to which older zoologists attrib- 

 uted too much importance. Brain, heart, the form of 

 the extremities, and the reproductive system, are indeed 

 distinct developments which, in combination with the 



