80 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 



merteans form no exception to this rule, as the few attempts made 

 at their collection attest. In the material at hand there are 28 spe- 

 cies, but this number doubtless rei)resents but a portion of those 

 which actually occur in those regions. It seems likely that more 

 than double this number will eventually be found there. A number 

 of species not yet recorded fi-om Puget Sound or British Columbia 

 have been collected both north and south of those localities. 



From the Pacific coast of Alaska, east of the Aleutian Islands, 33 

 species are recorded. Very little collecting has as yet been done at 

 or near the Aleutian Islands, and only 9 species are known from this 

 locality. On the Commander Islands, off the coast of Kamchatka, 

 at the Pribilof Islands and fi-om other })ortions of the Bering Sea, 

 9 species have been obtained, for the most part by means of the 

 dredge. From the Arctic Ocean but a single species is represented 

 in these collections, and that was obtained at two localities north of 

 70° N. Lat., or near the most northern ])oint of land in Alaska. 

 Several other forms, however, have been collected in Bering Strait, 

 and might, perhaps, have properly been included with the single 

 Arctic species. The ocean north of Bering Strait is, however, 

 practically unexplored for invertebrates. 



It is also worthy of note that 20 of the 86 species as yet known 

 from the Pacific coast have been found in southern California only, 

 and are not known to occur in the much colder water north of Point 

 Conception. On the other hand, 8 forms are common both to 

 Monterey Bay and southern California, but have not been met with 

 elsewhere. There are 16 species which extend from Alaska to 

 Monterey Bay, of which 8 extend the whole length of the coast from 

 Alaska to southern California. Some of these latter have a distribu- 

 tion of more than 5000 miles on the Pacific coast and Bering Sea 

 alone, besides being found in other portions of the world. This 

 range represents extremely varied environmental conditions, includ- 

 ing a difference in tem])erature of the water varying from that of 

 nearly constant summer temperature to one which is never more 

 than a degree or two above the freezing point. Such species are 

 usually remarkably hardy and occur in all sorts of situations from 

 half tide to a depth of a hundred or more fathoms. Extended geo- 

 graphical range is often correlated with al)ility to withstand very 

 varied conditions of local environment. 



On the whole, the observations on the distribution of the Pacific 



