1918J Esscnhevg: Distribution of the Fohjnoidae 203 



abruptly show the same corresponding gradual changes in faunal 

 distribution. 



Izuka (1912) shows that the Kyushiu Island is an important 

 boundary line of distribution. Numerous northern species cease to 

 exist south of Satsuma, and the southern species do not extend north 

 beyond that point. On the Pacific side, the island Kinkwasan forms 

 the boundary line of distribution of annelids. The cold water species 

 rarely extend south of Kinkwasan Island, and the warm water species 

 do not occur north of that island. Here again the chief factor, if not 

 the only factor, controlling distribution is temperature. This differ- 

 ence in temperature is caused by the cold and warm currents sweep- 

 ing past the Japanese Islands. The islands there form a natural 

 division line between the warm and cold oceanic areas. Hence it is 

 natural to find the northern species occupying the cold area on one 

 side of the island ; while on the other side of the island, in the warmer 

 area, the warm water species only occur. 



An evidence of the influence of temperature on distribution is the 

 fact that arctic littoral species of polynoids, with a few exceptions, 

 appear as deep water forms in warm oceans. On this coast a few 

 species of Polynoidae are known which inhabit the littoral areas in 

 the boreal zones, while nearer the equator, in warmer waters, they 

 inhabit greater depths. As examples may be cited the following 

 species: Gattyana aniundseni, Gattijana cirrosa, Harmotko'e multi- 

 setosa and Lepidonotus caelorus. 



Gattyana aniundseni has been found off Greenland, at about 77° 

 latitude, as a littoral form at a depth of 16 fathoms, while in lower 

 latitudes along the coasts of Alaska, it occurs in deeper waters between 

 50 and 100 fathoms depth (table 5). Comparing the temperatures of 

 the corresponding latitudes we find that the temperature in waters 

 of Greenland is about 0°, while near the Alaskan coasts, about 58° 

 latitude, it is about 1?4 to 2°. In a depth of 100 meters, however, 

 about 50 fathoms, the temperature at the latter latitude is 0?4 (see 

 tables 6 and 7), which is about identical with the temperature of the 

 shallow waters off Greenland. 



Gattyana cirrosa occurs in the Arctic oceans off Greenland and 

 Alaska, about 60° to 70° latitude, in depths of 10-12 fathoms, while 

 the same species occurs off the shores of Great Britain, about 55°N 

 latitude, at a depth of 600 fathoms. The surface temperature at the 

 coresponding latitudes differs considerably but the temperature of 

 600 fathoms depth off the shores of Great Britain is nearly identical 



