206 Universiiy of Valifornia Fiihlicatioiis i)i Zoology [Vot,. is 



These observations lead to the conclusion that the distribution of 

 Polynoidae, which occurs in a definite manner, is not a mere accident, 

 but that it is governed by some underlying principles or factors. One 

 of the chief controlling factors undoubtedly is temperature. 



III. Role of Currents in Distribution 



The locomotion of Polynoidae is by means of swimming and crawl- 

 ing, the latter method being the more common. If a polynoid is brought 

 to the surface of the water, it swims with undulating motions, soon 

 returning to the bottom. The writer has never seen an adult polynoid 

 rise to the surface under ordinary circumstances and swim, as many 

 other polychaetous worms do. Keeping various annelids in aquarium, 

 the writer has observed that some of them, e.g., Phyllodocidae, Nephthy- 

 didae, if disturbed rise to the surface and swim about vigorously, and 

 very often when the aquarium overflows the worms are found outside 

 of the aquarium. The Polynoidae, however, do not leave the aquarium 

 even when the latter overflows. This shows that they habitually live 

 on the bottom, crawling about slowly, searching for their food in the 

 mud and capturing other smaller animals or attacking one another. 



Since the Polynoidae are bottom dwellers and are not known to be 

 very powerful swimmers, how then shall we account for their wide 

 distribution? With their limited powers of locomotion they could 

 not possibly traverse distances of thousands of miles, yet the cosmopoli- 

 tan species occur in all oceans, as I have stated, from the Arctic Ocean 

 to and south of the equator (table 5). Some Pacific coast species as 

 Harmothoe liirsiita inhabit tlie northern subtropical zone along the 

 shores of southern California, but one example of this species, how- 

 ever, has been found on the coast of Chile. Harmothoe forcipata also 

 is known to occur abundantly on the coast of southern California 

 (Moore, 1910). One specimen has been found near Eno-Sima, Japan 

 (Ehlers, 1875), and another specimen has been found on the north 

 coast of Korea at a depth of 1400-1600 meters ( Marenzeller, 1902). 

 Harmothoe tuta has been reported from Sitka (Grube, 1855) and 

 from Puget Sound (Johnson, 1901). Harmothoe yokohamiensis has its 

 habitat along the coast of California (Moore, 1910), but one example 

 has been reported from Yokohama, Japan (Mcintosh, 1885). A num- 

 ber of examples of Gattyava senta have been taken on the southern 

 coast of California, but the same species has also been reported from 

 McCormick Bay, Greenland (Moore, 1902). Numerous cases of this 



