PLANKTON OF THE GULF OF MAINE 
57 
numbers of large Salpas (probably S. tilesii ) in Massachusetts Bay in November 
and December, 1913, which, so far as I can learn, are the only occasions when 
Salpse have been found in such numbers within the gulf, though they are often reported 
in abundance south and west of Cape Cod. Local swarms, such as this, probably 
result from their very rapid asexual multiplication (there is no evidence that they 
can reproduce sexually in cool waters) in summer and early autumn (A. Agassiz, 
1866). 
The Portuguese man-of-war (Physalia), with its translucent float, is even more 
apt to attract attention than Salpa, as it drifts on the surface, and it is equally a 
tropical visitor, though at the mercy of wind as much as of current. We have only 
one record of Physalia within the gulf, viz, in the eastern basin, June 19, 1915 
(Bigelow, 1917, p. 246; a single specimen seen but not captured). In the summer of 
1889, however, a year when Physalia was unusually plentiful off the coast of southern 
New England, many were seen in the Bay of Fundy and several were taken near 
Grand Manan and submitted to Doctor Fewkes for identification (Fewkes, 1889 
and 1890). The only other tropical coelenterates so far recorded within the gulf 
are two examples of the siphonophore Physophora hydrostatica on German Bank 
(station 10030) in August, 1912 (Bigelow, 1914, p. 103), 28 while the “Venus girdle” 
(Cestum), a warm-water ctenophore, is known from off the southeast slope of Georges 
Bank (Smith and Harger, 1874; Bigelow, 1914b, p. 31). 
We have one record for a tropical pteropod ( Limacina infiata ) off Cape Cod on 
July 19, 1914 (station 10213), while two living specimens of the pteropods Diacria 
trispinosa and Atlanta, genera that are of warm Atlantic if not strictly tropical 
origin (Meisenheimer, 1905), were taken in a haul near Gloucester on July 8, 1913. 
The warm-water hyperiid amphipod PJironima sedentaria was taken on Browns 
Bank on June 24, 1915 (station 10296), which, with a fragment of gulfweed near 
German Bank (September 2 of that year), completes the list. 
The geographical locations of these records, the most characteristic of which are 
shown on the accompanying chart (fig. 31), and their dates prove that occasional 
planktonic immigrants from the inner edge of the Gulf Stream may be expected 
anywhere in the Gulf of Maine at any season. Aside from Thysanoessa gregaria, 
however, which may, perhaps, be endemic in small numbers in our waters, or which 
at least is able to survive there for a long time if it does not reproduce (p. 143), and 
omitting Sagitta serratodentata, which falls in a different category (p. 58), there is a 
decided preponderance of tropical records in the eastern part of the gulf, though 
fewer hauls have been made there than in the western, a concentration, that is to 
say, where the salinity curves locate the chief influx of offshore water. The great 
majority of the records lie in the peripheral zone corresponding to the anticlockwise 
oceanic eddy that dominates the circulation of the gulf. 
In spite of the considerable tropical list, we have never made anything that could 
be called a tropical haul in the gulf or encountered a community of animals of warm- 
water origin there. In fact, most of the records are for single specimens; seldom has 
the tow net yielded as many as half a dozen at any one station, and, except for certain 
28 Also taken off the southern face of Georges Bank on July 24, 1916, station 10352. 
