266 PROFESSOR EDUARD SUESS 



more particularly of Vienna. Here one recognizes the following: 

 Living beings are dependent, on the one hand, on certain outer 

 physical circumstances, as climate, moisture, etc.; on the other 

 hand, they also are mutually and socially dependent upon one another. 

 Every living province — or, as it is usually expressed, every zoologi- 

 cal province — forms, as it were, an economical unity in which for 

 so many flesh-eaters there must be so many plant-feeding food 

 animals; for so many plant-feeders, so many food plants; honey- 

 sucking Lepidoptera presuppose flowers; for insect-feeding song- 

 birds a certain number of small insects are necessary, etc. The 

 disturbance of one member of this unity can possibly destroy the 

 balance of the whole. 



According to all appearances, such disturbances have occurred 

 from time to time in land faunas, and they may have been of very 

 diverse kinds. Then again an entire fauna is seen to vanish over 

 all Europe, or over a still greater region, and a new fauna comes in 

 to take its place. This new fauna nevertheless always has a more 

 or less strongly vicarious relationship to its predecessor; it is clearly 

 a variation of the former, probably in the main a resulting adap- 

 tation to changed conditions; and even if the sequence of strata 

 were completely unknown, one could readily discern which was the 

 first, the second, or the third fauna. 



Besides this, the numerous phylogenetic lines which unite nearly all 

 the great groups of fossil animals; or the unity in the developmental 

 nature of single organs, as the extremities; or the general super- 

 position of gills and lungs; or the rows of striking harmonies that 

 exist between the development of certain groups of animals, and 

 of single individuals of these groups — all indicate with certainty the 

 correctness of the Darwinian basal idea, namely, the unity of life. 



Stratigraphic geology and paleontology show that the evolution 

 of organic life was probably never completely interrupted, but that 

 it did not go on in a uniform manner. Disturbances have occurred. 

 The struggle for existence continues; yet it is only of secondary 

 importance. Single very old types, as Hatter ia (S phenodon) , have 

 continued to maintain themselves to our day with but slight changes. 



Allow me now to speak of a few tectonic questions. 



When I began my collegiate work, there prevailed, especially in 



