lW-2.] DAVIS — SYSTEMATIC GEOGRAPHY. 255 



ing therefore as the geographical plane is placed nearer to one 

 framework or to the other, the presentation of the total subject 

 might be made primarily physiographic and secondarily ontographic, 

 or the reverse. 



19. Subdivisions of Ontography. — It is not an ontographic classi- 

 fication, but the nature of such a classification that can here be set 

 forth to best advantage. There should be two chief subdivisions ; 

 the first includes those responses that were initiated ages ago and 

 maintained by inheritance till to-day because their controls are 

 persistent; the second, those of relatively recent origin. Further 

 subdivision might be made in accordance with the standard classi- 

 fications of botany and zoology, in which the responses of all kinds 

 of plants and animals to physiographic controls would be taken up 

 in their natural order. But in view of the repetition of similar 

 responses in many different classes of organisms, it will be here 

 more convenient to follow a physiographic order in the ontographi- 

 cal classification. Examples of long-inherited responses will be 

 mentioned first. 



As inhabitants of an earth whose mass is very much greater than 

 that of all its organic population, plants and animals very generally 

 show a response to the action of gravity in their attitudes as well 

 as in their structure. As inhabitants of an earth whose opaque 

 surface is illuminated from without, the distribution of color in 

 plants and animals is often closely associated with the response to 

 the downward action of gravity. As occupants of an earth whose 

 surface is nearly globular, plants and animals have been allowed a 

 much wider migration than would be possible for the occupants of 

 a very irregular body, on whose surface gravity would vary greatly. 

 None of these responses are doubtful as to origin or difficult as to 

 comprehension ; they ought to be introduced in the elementary 

 study of the earth as the globe ; and their almost universal omission 

 from that chapter of geography affords immediate illustration of the 

 little thoroughness with which the subject is treated. Perhaps 

 these matters have been omitted because they are regarded as of 

 less importance than the names of the branches of Siberian rivers ; 

 but if so, a very singular standard for the measure of importance 

 has been accepted. Many other long-inherited responses to the 

 physical features of the earth as a globe might be instanced, but 

 space is lacking for their presentation. 



One of the most universal of all organic habits, that of breathing 



PROC. AMER. PHILOS. SOC. XLI. 170. Q. PRINTED SEPT. 24, 1902. 



