204 THE DESCENT OF MAN. Part I. 



Nevertheless it is certain that groups of animals have 

 existed, or do now exist, which serve to connect more or 

 less closely the several great vertebrate classes. We 

 have seen that the Ornithorhynchus graduates towards 

 reptiles; and Prof. Huxley has made the remarkable 

 discovery, confirmed by Mr. Cope and others, that the 

 old Dinosaurians are intermediate in many important 

 respects between certain reptiles and certain birds — the 

 latter consisting of the ostrich-tribe (itself evidently a 

 widely-diffused remnant 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, 20 the Ichthyosaurians — great sea-lizards fur- 

 nished with paddles — present many affinities 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 swarmed during the earlier geological 

 periods, and were constructed on what is called a highly 

 generalised type, that is they presented diversified affi- 

 nities 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 Lepidosiren and 

 some few Ganoid fishes have been preserved from utter 

 extinction by inhabiting our rivers, which are harbours 

 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 lancelet or amphioxus, 

 is so different from all other fishes, that Hackel main- 

 tains that it ought to form a distinct class in the 

 vertebrate kingdom. This fish is remarkable for its 



20 ' ralceontoiu-v,' 1860, p. 199. 



