2 SURFACE FAUNA OF THE GULF STREAM. 
will be seen, they have much less in common. This group of Hydrozoa is 
eminently characteristic of the Gulf Stream, and wherever its influence 
extends there Porpitz, Velella, and Physalie have been found. In fact 
these surface animals are excellent guides to the course of the current of 
the Gulf Stream, — natural current bottles, as it were. They are thrown 
up along the whole length of the Atlantic Coast of the United States, from 
the Straits of Florida to the south shores of Cape Cod and of Nantucket. 
Physalia, Velella, and Porpita are occasionally driven into Narragansett Bay ; 
the former is an annual visitant, the latter has only been found once, in 1875, 
and Velella has come into Newport harbor during three summers. It is 
undoubtedly also to the action of the Gulf Stream that we must ascribe the 
presence of the few species of Siphonophorz which appear on the southern 
coast of New England towards the middle and last of September, such as 
Eudoxia, Epibulia, and Dyplophysa, which are all found at the Tortugas. 
On the contrary, Agalma and Nanomya are northern visitants at Newport, 
brought down by the arctic shore current from the northern side of Cape 
Cod, Agalma being common at Eastport. Other species of our southern New 
England free Hydroids, such as Eutima, Trachynema, Eucheilota, Liriope, 
Zanclea, and many other species which have been described by McCrady, 
from Charleston, 8. C., are also brought north every year along the course 
of the Gulf Stream, and during the summer are blown to the westward 
towards the New England coast and the Atlantic coast of the Middle States 
by the prevailing south-westerly winds. 
Velella mutica Bosc. 
The Florida species of Velella occasionally finds its way north as far as 
Newport and Nantucket; it is found in great numbers in the Straits of Florida, 
between Cuba and the Florida reefs. Thousands of them are brought in by 
favorable winds and tides into Key West harbor, and are carried by the same 
agencies between the Tortugas channels. They are usually seen in large 
schools, and, although capable of considerable independent movement, by 
means of their tentacles, in a smooth sea, yet they are practically at the 
mercy of the winds and currents. They are destroyed in great numbers by 
even moderate waves, which, upsetting them, drive them ashore, or kill 
them, if they are kept keel downward for any length of time. They appar- 
ently need a considerable amount of movement, for when kept in confine- 
ment they do not thrive, soon die, and are rapidly decomposed. The dead 
