Perspectives in sensory-ecological studies of higher vertebrates.

It is firstly recalled that, among Vertebrates, in peripheral sense-organs on the one hand, in encephalic relays and terminals on the other hand, not only the types but also the numbers of neurons, are determining factors for the kinds of relations that exist between organisms and environments. It is thus necessary to consider the quantitative developments of relay-stations and the volumes of brain-components when studying such relations. The very concept of sense-organ may even have to be broadened, because it should include central transmission structures along with peripheral starting points. It is stressed that progresses achieved by Vertebrates in the course of their history by quantitative increases of either terminals or relays should be labeled either as specializations or as evolutions, for these two concepts must not be confused.