THE AMERICAN NATURALIST [Vol. XLII1 



The surface temperatures of the Peruvian current, as 

 related to those of the Magellanic water, are therefore 

 warmer; and, as compared with the Panamic waters, 

 markedly colder. Precisely such a relation to the coast 

 of North America is held by the southerly branch of the 

 North Pacific current, which reaches the coast near Sitka 

 with a summer temperature of 65° to 68°. This has 

 diminished in the latitude of San Francisco Bay to 54 °F., 

 but the current continues until in the vicinity of Point 

 Conception, California, it is diverted off shore in a man- 

 ner entirely analogous to the fate of the Peruvian current 

 at Point Aguja. 



The water of the Panamic Province is less disturbed 

 by currents, receives the full heat of the tropical sun, and, 

 as shown by Professor Alexander Agassi z, emerges from 

 the Gulf of Panama, follows the coast toward Cape San 

 Lorenzo, and is there diverted off shore toward the Gala- 

 pagos Islands. Trees from the mainland with leaves 

 still adhering to them are occasionally cast upon the 

 shores of the Galapagos, as observed by Professor Agas- 

 siz ; showing clearly that the current is not only present 

 but has no inconsiderable motion. The temperature of 

 this water near the coast of Keuador and only a few miles 

 from the limit of the Peruvian current, in November, 

 varied from 70° to 83° F., and in March and April from 

 78° to 85° F. Among the Galapagos Islands the range in 

 April was 81° to 83° F. 



It will be noticed therefore that the currents fully 

 account for the peculiarities of the Galapagos mollusk- 

 fauna, which exhibits large contributions from the Pan- 

 amic and Peruvian faunas with only a very unimportant 

 tincture of the Indo Pacific in its make-up. 



A series of surface temperatures measured in Novem- 

 ber at right angles to the Peruvian current off Point 

 Aguja, by the IT. S. S. Albatross, began with a tempera- 

 ture of 65° F. close in shore, rose quickly to 69° and later 

 to 70° in the middle of the current, and declined again to 

 69° F. on its western edge. 



