484 EEPOET OF COMMISSIONER OF FISH AND FISHERIES. 



RADIATA. 



Hydroids. 

 Page. 



•Obelia gelatinosa 482 



O. pyfiformis 390 



O. diaphana 327 



Polyps. 



Halecium gracile 328 



Parypha crocea 482 



Page. 



Sagartia leucolena 329 



Page. 

 Metridium marginatum 329 



IY. — FATTNA OF THE OCEAN SHORES AND OUTER COLD WATERS. 



All along this coast, fjom Cape Cod to Stonington, Connecticut, there 

 is a belt or current of cold water which impinges directly against the 

 outer islands and the open coast, especially where there are points of 

 land projecting outward toward the deeper waters. This is especially 

 noticeable at Gay Head, on Martha's Vineyard, No Man's Land, Cutty- 

 hunk Island, Montauk Point, Block Island, Point Judith, and Watch 

 Hill. This cold water is undoubtedly derived from the Arctic current, 

 which passes slowly southward in deep water off our coast, but whether 

 an actual current, distinguishable from the tidal currents, exists in the 

 waters of moderate depth along the coast is still uncertain. The tidal 

 currents apparently have the effect; of bringing the cold water of the 

 outside regions up into the shallower localities along the shores, and it 

 is probable that the presence of the cold water in moderate depths is 

 due to the joint action of the tides and the slow-moving Arctic current, 

 which impinges more or less against and upon the slope of the sub- 

 merged eastern border of the continent. But the position, extent, and 

 temperature of this cold water along our shores varies greatly, accord- 

 ing to the direction of the tidal currents and the surface currents 

 caused by the wind. We have shown, on a former page, that at times 

 these local winds and tidal currents are able even to bring Gulf Stream 

 water and its characteristic animals directly upon this coast, even as far 

 westward as Watch Hill, Khode Island, where the Physalia is often cast 

 ashore in summer. At such times the cold current must necessarily be 

 wholly displaced, or disguised by intermixture with the warmer waters. 

 When the tide is flowing from Long Island Sound, Vineyard Sound, or 

 other large bodies of warm water, the cold waters will also be displaced 

 and the temperature raised even at the distance of twenty or thirty miles 

 from the shore in summer. In winter there is comparatively little 

 effect from the Gulf Stream, owing to the prevalence of northerly winds, 

 and there is also far less effect from the warm waters of the shallow 

 bays and sounds carried by the tides. Therefore the full effect of the 

 northern current is felt only in winter, and it doubtless adds to the cold 

 proper to the season and land climate. 



In winter and early spring we accordingly find numerous species ot 

 northern animals and algoe which disappear partially or wholly in many 



