PLANKTON OF THE GULF OF MAINE 
53 
TROPICAL VISITORS 
The term “tropical visitors” is used here for such animals as are native to the Gulf 
Stream and are able to survive only in its warm surface waters outside the edge of 
Fig. 31. — Locality records for certain of the more typical planktonic animals of tropical or warm-Atlantic origin. A. Salpae, 
®, Thysanoessa gregaria ; X, tropical copepods; O, Portuguese man-o-war (Physalia); A Physophora hydrostalica ; 
O, gulf weed (Sargassum); ™, many tropical species 
the continent. Others equally of tropical origin, but which find conditions more 
favorable for growth (though not for reproduction) in the mixed water, are discussed 
as belonging to the latter, for it is by that route that they enter the Gulf. 
