174 Uiiiversitij of California Puhlicatio)is in Zoology [Vol. 18 



C. POLYNOIDAE AND THEIR GENERAL DISTRIBUTION 



The Polynoidae, one of the families of the scal.y annelids, pass the 

 first stage of their life as trochophore larvae. The eggs, after leaving 

 the body cavity of the worm, are attached by a mucous secretion to 

 each other and to the dorsal surface of the parent's body beneath the 

 scales. There they develop until a preoral band of cilia is formed, 

 when the larvae escape as the well known trochophores swimming 

 freely near the surface of the water. The larvae finally settle to the 

 bottom of the ocean, undergoing there further metamorphosis and 

 assuming gradually the shape of the adult worm. Thus during its 

 embryonal development, the stage of the greatest susceptibility, the 

 polynoid is subjected to considerably varied environmental conditions. 



Polynoidae as a group are cosmopolitan in their distribution, rang- 

 ing from the arctic to the equatorial and to the antarctic regions, 

 inhabiting the littoral as well as the abyssal zones. However, the 

 same species may not be represented in all of these regions. 



I. Horizontal Distribution 



On the basis of distribution the Polynoidae may be divided into 

 two main groups: (1) the cosmopolitan polynoids; and (2) poly- 

 noids limited to restricted areas. These groups, especially the latter, 

 may be again separated into a number of subdivisions, according to 

 the areas they inhabit, as will be shown in the following pages. 



Of the fifty-one species of Polynoidae known up to the present 

 time from the Pacific coast of North America, two species, or about 

 four per cent, are cosmopolitan. These two species are Harmothoe 

 imhricata and Lcpidonofus squamatns. The former is known to occur 

 in all European oceanic waters. Marenzeller (1902) describes it from 

 the coasts of Japan. Other workers record its distribution from Cape 

 Cod to the St. Lawrence, from Siberia, Greenland, Iceland and from 

 Scandinavia. Its presence has been recorded in the Okhotsk Sea and 

 in other parts of the Arctic Ocean. It also occurs in great abundance 

 along the Pacific coast of North America from Alaska to San Diego, 

 California. 



Lppidonotus sqiianiatus occurs in great abundance in the Atlantic 

 Ocean along the shores of Great Britain and in Canadian and Ameri- 

 can waters. It has been found ofi' the Azores at a depth of 450 

 fathoms (Mcintosh, 1900). Although it does not occur in great 

 abundance along the coast of California, nevertheless, specimens have 



