36 MARINE BIOLOGICAL LABORATORY. 



in their adult condition, if they pass through closely 

 similar embryonic stages, we may feel assured that they 

 are all descended from one parent-form." Thus embry- 

 ology came to have a higher value in classification than 

 anatomy, and to take the place assigned to it by v. Baer 

 more than half a century ago, as ''the true torch-bearer 

 in the investigation of organic bodies." 



Embryology and paleontology have become comple- 

 mentary sciences, associated in the common aim of 

 determining the genesis and the history of life. The 

 peculiar charm of embryology is, that it brings us into 

 direct contact with living forms, places us face to face 

 with the phenomena of life, and reveals in the history 

 of the individual the principal events in the history of 

 the race. It holds the key to many a problem that 

 has exhausted the resources of all the sister branches 

 of biology, and promises to contribute more than all 

 the rest towards the solution of the great mystery 

 of life. 



In order to illustrate the relative position of embry- 

 ology, and at the same time the nature of the naturalist's 

 work, let us now look at one of the problems before 

 him. 



II, A Special Problem. 



Naturalists are familiar with the efforts of compara- 

 tive anatomy to determine the number of segments in 

 the vertebrate head. At the beginning of this century, 

 Germany's great poet, Goethe, and one of her most gifted 

 naturalists, Oken, came independently to the idea that 

 the skull is only an enlarged and otherwise modified 

 portion of the backbone ; that is, that it is composed of 



