PEDIGREES. 169 



fection, whilst the adult shark has not far out- 

 stretched the condition of its babyhood. This 

 advance from the simple to the complex, which 

 takes place in the course of the life history of the 

 salmon, is illustrated again in the life history of 

 the development of the race of fishes, the simpler 

 forms, such as the shark tribe, appearing earlier 

 in the world's history than the more complex 

 bony fishes, of which we have taken the salmon 

 as a type. The gradual advance in complexity 

 of structure and variety of form which has taken 

 place since the appearance of the early fishes, we 

 call their evolution. 



One word more; we shall discuss fossil and 

 recent forms indiscriminately, both in the fol- 

 lowing and all other orders of fishes, for, as Dr 

 Traquair pertinently remarks, "Does an animal 

 cease to be an animal because it is preserved in 

 stone instead of spirits ? Is a skeleton any the 

 less a skeleton because it has been excavated 

 from the rock instead of prepared in a macerating 

 trough ? And I may now add, Do animals, be- 

 cause they have been extinct for it may be 

 millions of years, thereby give up their place in 

 the great chain of organic beings, or do they 

 cease to be of any importance to the evolutionist 

 because their soft tissues, now no longer existing, 

 cannot be embedded in parafin and cut with a 

 Cambridge microtome." 



The sharks and rays, though belonging to 

 an ancient and lowly organised group, are of 

 that group exceedingly specialised forms. The 

 evidence of specialisation here is found in the 

 changes which have taken place in different 



