INVERTEBRATE ANIMALS OF VINEYARD SOUND, ETC. 437 



surface, being sometimes a little lower and sometimes higher than that 

 of the surface, but generally the same. The higher temi)eratures 

 usually occurred with, or following, southerly or southeasterly winds, 

 (from the direction of the Gulf Stream,) while the lowest ones gener- 

 ally accompanied or followed northerly winds. The tides must ob- 

 viously also have some effect in modifying the temperature. 



It must not be inferred from the preceding remarks that a distinct or 

 constant current flows into these waters from the region of the Gulf 

 Stream, for the facts do not warrant such a belief, nor is there any dif- 

 ficulty in explaining the ])henomena in another way. All that is neces- 

 sary to account for the higher temperatures of this region, and the fre- 

 quent occurrence of Gulf Stream animals, is to suppose that when 

 southerly or southeasterly winds blow continuously for a considerable 

 time they cause a superficial flow or drift of warmer water from the 

 Gulf Stream region tow^ard these shores, which may also be aided by 

 the tides ; such a surface-drift will graduall^^ lose its distinctness as 

 it approaches the coast and mingles more and more with the cooler 

 waters beneath, but the animals borne along by it will still serve to 

 show its direction and origin, even after its temperature becomes iden- 

 tical with that of the adjacent waters. Such surface currents would 

 necessarily be intermittent in character and variable in direction and 

 extent, as well as in duration and temperature. They would also be 

 more frequent in summer than in winter, according with the prevalent 

 direction of the winds. So far as known to me all the facts are in 

 harmony with this view. Accordingly the waters of Vineyard Sound 

 are* quite cold in winter, and onl}^ occasionally receive a little heat from 

 the Gulf Stream region, and that, probably, largely through the medium 

 of the air itself; but in summer these waters are very warm, for they 

 not only receive frequent accessions of warm water from the Gulf 

 Stream, but they are also favorably situated to be rapidly warmed by 

 the direct heat of the sun. 



The fauna of the surface in this region is very rich and varied, es- 

 pecially in summer. In winter, life is also abundant in the surface 

 water's, but very diftereut in character from that found in summer. 

 Had collections been made in spring and autumn, still other groups of 

 animals would doubtless have been found. Our knowledge of the surface 

 animals of Vineyard Sound, in winter, is wholly based on aseriesof surface- 

 dredgings made by Mr. Vinal N. Edwards in January, February, and 

 March of the past winter. A separate list of the species contained in 

 these collections, so far as identified, has been prepared to follow 

 the general list. The most noticeable feature of the winter collections 

 is the entire absence of the larval forms of crabs, shrimps, lobsters, 

 star-fishes, sea-urchins, annelids, &c., which so abound in the same 

 waters in summer. On the other hand there is a great abundance of 

 Entomostraca, Sagltta, several northern Amphipods, species of Mysis , 

 v&c., together with eggs and young of certain fishes. 



