24 CALIFORNIA ACADEMY OF SCIENCES TProc. 4th Ser. 



apparently present in the case of the tropical pelecypods and 

 gastropods, and the slow changes of fauna are apparently pro- 

 duced by slight changes in temperature, depth, salinity, and 

 food. In other words, the "wonderful stability of protoplasm" 

 seems to be exhibited in these marine tropical invertebrates 

 except when environmental changes impress alterations upon 

 this vital life substance. 



Crowding of Species and the Recent Fauna of the 

 Philippines 



A seeming objection to the main thesis of this paper is found 

 in connection with the great abundance of species in the marine 

 waters surrounding the Philippine Islands. As was mentioned 

 above, climatic zones were by no means as sharply differen- 

 tiated during the early as during the later portion of the Ter- 

 tiary. Practically all Recent tropical genera were initiated in 

 the Eocene, and many of the species representing these genera 

 had, during this period, an exceedingly wide geographic range, 

 particularly as respects latitude. During this time tropical 

 species flourished in high latitudes. To use a simple comparison, 

 the tropical life "accordion" was extended to its greatest limit. 

 The exact nature of the change which caused a separation of 

 remarkable distinctness between the Oligocene faunas of the 

 Pacific Coast of North America from the Eocene is not fully 

 understood. It seems probable however that the time repre- 

 sented by unconformity between Oligocene and Eocene was 

 long. The distribution of land masses on the earth was pro- 

 foundly affected, and it seems quite probable that the climate 

 during this ep-Oligocene time was decidedly cooler than in the 

 Eocene or the Oligocene which followed. It seems quite prob- 

 able that the life "accordion" was compressed and many species 

 which ranged far to the north in Eocene time were compelled 

 to seek the more genial climes of the tropic seas. When the 

 faunas during the Oligocene again had a chance to expand into 

 higher latitudes, they encountered new conditions of environ- 

 ment and were nearly all specifically changed. The Oligocene 

 faunas of Oregon, Washington, and California are distinctly 

 set off from the Miocene and similar changes may have taken 

 place during ep-Miocene time. Again many of the species sue- 



