[437] INVERTEBRATE ANIMALS OF VINEYARD SOUND, ETC. 143 
surface, being sometimes a little lower and sometimes higher than that 
of the surface, but generally the same. The higher temperatures 
usually occurred with, or following, southerly or southeasterly winds, 
(from the direction of the Gulf Streain,) 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 phenomena 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 toward these shores, which may also be aided by 
the tides; such a surface-drift will gradually 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 only 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 
pot 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 
waters, but very different 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 aseries of 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, Sagitta, several northern Amphipods, species of Jlysis, 
&c., together with eggs and young of certain fishes. * 
