204 University of California Publications in Zoology [Vol. is 



with the surface temperature off Greenland and that of the coasts of 

 Alaska. 



Harmothoe multisetosa is found in the lower boreal zone, along 

 the shores of Alaska, in depths of from 18 to 23 fathoms. In the 

 temperate and subtropical zones it occurs in depths varying from 50 

 to 750 fathoms. It is more abundant beyond the 500 fathom line, 

 only one case at a depth of 50 fathoms having been reported from 

 Monterey Bay where the species occurred. Off Cape Colnett, in Lower 

 California, however, the species occurs in 1,400 fathoms depth. Again, 

 comparing the temperatures of the corresponding latitudes and the 

 depths (tables 6 and 7) given in connection with the distribution, we 

 find that the species, although occupying widely separated areas and 

 different depths, lives in identical temperatures, and evidently for 

 that very reason is found in deep waters in the subtropical regions, 

 where the temperature is the same as that of the shallow waters of 

 subboreal regions. With a farther advance toward the tropical regions, 

 its habitat extends to greater depths, and this is true of the tempera- 

 ture (table 6). In order to find the temperature identical with that 

 of the Arctic waters, one must seek it in deeper and deeper water as 

 he approaches the equator. 



Another species, Lepidonotus caclorus, occurs in abundance and in 

 various depths on this coast mostly between 70 and 500 fathoms. Off 

 Cape Colnett, Lower California, the species occurs at a depth of 1,400 

 fathoms. The temperatures of the various depths occupied by this 

 species, however (table 6), are identical. These facts seem to prove 

 that species, although they may occupy widely separated geographical 

 areas, do live in identical temperatures. [Speaking of identical tem- 

 peratures, one has to keep in mind that the temperature of an entire 

 life zone, and not of one particular point is considered ; consequently 

 an allowance for variation in temperature of about five degrees or 

 more should be made.] Similar observations were made by Ehlers 

 (1875) who found that Arctic species of annelids outside of the Arctic 

 realm always inhabited considerable depths, and were never found at 

 the depths frequented by the same species in colder regions. This was 

 shown remarkably well in some parts of the Norwegian Sea, where 

 near shore the temperature is constant, ranging from 6° to 7°. Ap- 

 proaching the deeper basin of 600 meters the temperature is about 0°, 

 or identical with the temperature of Arctic waters. A corresponding 

 difference in distribution of annelids was also found there. In the 

 warmer areas, nearer shore, were found the warm water annelids which 



