196 THE DESCENT OF MAN. [Part I. 



seeu that the Ornitliorliynclius graduates toward reptiles ; 

 and Prof. Huxley lias made the rcmarkahle discovery, 

 confirmed by Mr. Cope and others, that the old Dinosaii- 

 rians are intermediate jn many important respects between 

 certain reptiles and certain birds — the latter consisting of 

 the 'ostrich-tribe (itself evidently a widely-diffused rem- 

 nant of a larger group) and of the Archeopteryx, that 

 strange Secondary bird having a long tail like that of the 

 lizard. Again, according to Prof Owen,"" the Ichthy- 

 osaurians — great sea-lizards furnislied with paddles — pre- 

 sent many afiinities with fishes, or rather, according to 

 Huxley, with amphibians. This latter class (including in 

 its highest division frogs and toads) is plainly allied to 

 the Ganoid fishes. These latter fishes swarined during 

 the earlier geological periods, and were constructed on 

 what is called a highly-generalized ty|>e, that is, they pre- 

 sented diversified affinities with other groups of organisms. 

 The amphibians and fishes are also so closely united by 

 the Lepidosiren, that naturalists long disputed in which 

 of these two classes it ought to be placed. The Lepido- 

 siren and some few Ganoid fishes have been preserved 

 from utter extinction by inhabiting our rivers, which are 

 harbors of refuge, bearing the same relation to the great 

 waters of the ocean that islands bear to continents. 



Lastly, one single member of the immense and diver- 

 sified class of fishes, namely, the lancelct or amphioxus, is 

 so different from all other fishes, that Ilackel maintains 

 that it ought to form a distinct class in the vertebrate 

 kingdom. This fish is remarkable for its negative charac- 

 ters ; it can hardly be said to possess a brain, vertebral col- 

 umn, or heart, etc. ; so that it was classed by the older 

 naturalists among the womis. Many years ago Prof 

 Goodsir j^orceived that the lancelet presented some affini- 

 ties with the Ascidians, which are invertebrate, hermaphro- 



•0 Talicontology,' 1800, p. lO.). 



