34 MARINE BIOLOGICAL LABORATORY. 



Thus you see how far from the surface the truth may- 

 lie, and how, in the systematic position of a single form, 

 we tnay find a problem which only yields to solution 

 after exhausting the resources of nearly every depart- 

 ment of animal biology. 



In order to correct and extend the results of surface 

 observation, the investigator appeals first to internal 

 structure, and is thus led into the province of anatomy. 

 Here fundamental features of relationship are brought 

 more clearly into view ; and, following the general 

 law that animals or plants of like structure have de- 

 scended from common ancestors, it becomes possible 

 to outline, in a rough way, a genealogical system. It is 

 here that the investigator would begin to grasp the 

 meaning of those deeper resemblances, called homolo- 

 gies, and learn to distinguish between these and decep- 

 tive analogies. But nature has concealed many of her 

 more important homologies under disguises that a study 

 of adult structure could not penetrate. Comparative 

 anatomy, in the hands of such men as George Cuvier, 

 Friedrich Meckel, Johannes Miiller, Richard Owen, 

 Thomas Huxley, and Carl Gegenbaur, has accomplished 

 wonders in this direction, but it owes many of its greatest 

 discoveries to the aid of embryology and paleontology. 

 Its greatest achievement was the .reduction of the 

 animal world to four great types, and the same high 

 elevation was reached independently by comparative 

 embryology. 



But the type system of George Cuvier and Carl Ernst 

 von Baer did not finish the reconstruction of the genea- 

 logical tree ; for it failed to grasp the full meaning of like 

 development and like structure. Comparative anatomy 



