428 
ORIGIN OF LIFE IN AMERICA 
and from it streamed forth practically all life, which eventually 
reached the most southern tips of the continents. We thus not 
only find there the oldest forms congregated together, accord¬ 
ing to Professor Dahl, but these would naturally resemble one 
another in all the southern parts of the continents. It is 
a simple theory, and at first sight, as I mentioned before, 
when discussing the similar views of Dr. Haacke, it seems 
to put before us the solution of all the problems of dispersal 
in a satisfactory manner. No one, however, who has taken 
the trouble to read this book, can for a moment, I venture to 
think, perceive any justification for holding such a belief as 
that of Professor Dahl’s. There may possibly have been such a 
centre of dispersal as that suggested, but it was long before 
any geological records existed. Any forms of animal life that 
we are acquainted with show clearly and unmistakably that 
there have been scores of great centres of dispersal in the 
world, and that from them streamed forth new forms in every 
available direction. Northern animals advanced southward 
and southern forms northward, aided, no doubt, by the ever- 
changing conditions of climate and the gradual evolution of 
oceans and continents. 
To return to the question at issue, let us examine what light 
the marine fauna throws on the problem. The geographical 
distribution of the elephant seal (Macrorhinus leoninus), 
which occurs on the shores of southern South America, of 
the antarctic lands, of New Zealand and Tasmania, will not 
contribute much to its solution, but some of the inverte¬ 
brates are of more importance. The Eocene beds of Pata- 
gonia, as well as those of New Zealand, contain several species 
of marine mollusks common to both, such as Cucullaea alta, 
Scalaria rugulosa and Turritella ambulacrum. Other Pata¬ 
gonian species, for example, Brachydontes magellanica, Tur¬ 
ritella patagonica and Crepidula gregaria only appear in New 
Zealand in later deposits. Besides these species the older 
Tertiaries of the two countries have a large number of genera 
common to both. Dr. von Ihering* thus concludes with con¬ 
siderable justification that the geographical conditions during 
early Tertiary times must have been favourable for a dis- 
Ihering, H. von, “ Mollusques Fossiles de L’Argentine,” p. 499. 
