200 University of Calif onda FiiMications in Zoology [Vol.18 



Schott and Scliu (1910) have tabulated the temperatures of the 

 various depths and latitudes from depths of meters to 4,000 meters 

 and from 60°N latitude to 50° S latitude. Their table and the map of 

 the Pacific coast give a very good idea of the distribution of the tem- 

 perature in the different depths and latitudes (see tables 6 and 7). 

 Comparing some of the data in this table we find that the tempera- 

 tures of the various depths near the equator correspond to the tem- 

 peratures of the various latitudes. The temperature at a depth of 

 3,000 meters near the equator corresponds to the surface temperature 

 of 60°N latitude. The temperature of the water at a depth of 1,500 

 meters is identical with the surface temperature at 55° latitude. The 

 temperature at 1,000 meters depth at 0° latitude is equal to the sur- 

 face temperature of 50° latitude. The temperature in the depth of 

 400 meters is equal to the surface temperature at 40° latitude. The 

 temperature at 200 meters at 0° latitude is equal to the surface tem- 

 perature of 30° latitude, and the temperat^^re in the depth of 100 

 meters at 0° latitude is identical witli the surface temperature of 

 20° latitude. 



II. Temperature as a Factor Controlling Distribution 



The above facts show that the vertical distribution of the tempera- 

 ture from the surface to the bottom in the lower latitudes is com- 

 parable to the horizontal distribution from the equator to the poles. 

 In some places along the coast the changes in temperature are so 

 abrupt that definite geographical points serve as division lines of 

 different isothermal areas. If the distribution of certain species of 

 animals and plants coincide with the distribution of the temperature 

 zones, as has been observed to be the case, it is obvious that the tem- 

 perature may be regarded as one of the main factors controlling the 

 distribution of Polynoidae. 



It is a well known fact that a strong heat in summer may kill all 

 the shallow water plants within a few days by raising the temperature 

 beyond the maximum which those plants can stand. Many organisms 

 of phytoplankton occur in shallow water in winter, but in deep water 

 during summer. The phytoplankton in the Gulf of Naples was not 

 found in surface layers but in a depth of 200 fathoms where the water 

 is considerably cooler, while in the oceans of higher latitude, as in the 

 North Sea, where the surface temperature is lower, the diatoms and 

 Peridiniae are found at the surface. In these regions, again, the depth 



