54 '. MARINE BIOLOGICAL LABORATORY. 



Of the numberless genealogical inquiries raised by the 

 theory of organic evolution, none has a higher interest 

 or has attracted more general attention than the deriva- 

 tion of vertebrates, involving, as it does, the origin of all 

 the highest manifestations of vital structure and action. 

 So long as the evolution tneory remained an unproved 

 and comparatively vague hypothesis, as it was left by 

 Lamarck and St. Hilaire sixty years ago, the origin of 

 vertebrates, like other genealogical inquiries, could have 

 no more than a speculative interest, and could produce 

 little direct effect upon morphological investigation — 

 which indeed had quite enough to take care of at home, 

 without following speculative zoology in her erratic excur- 

 sions. When, however, the field of action had been 

 cleared by such pioneers as von Baer, Johannes Miiller, 

 Remak, and Kowalevsky, when speculative zoology had 

 been redeemed and vitalized by Darwin, and the theory 

 of organic descent established on a firm footing, mor- 

 phological research entered upon a new phase. A broad 

 foundation of known facts had been laid ; a splendid 

 working hypothesis had been found. The central ques- 

 tion in every morphological investigation became two- 

 fold ; it was no longer simply wJiat is f it was also Jiow 

 came it to be? And this second question, be it observed, 

 is not properly a speculative matter at all, but an his- 

 torical one ; it relates not to an ideal or hypothetical 

 mode of origin, but to a real process that has actually 

 taken place in the past and is to be determined like 

 any other historical event. " Speculative zoology " 

 thus, by slow degrees, became the guide and leader of 

 research, and every morphological inquiry became, in 

 the last analysis, a genealogical one. 



