BIGELOW: COAST WATER EXPLORATION OF 1913. BOD 
GuLF oF MAINE PLANKTON, 1912 anv 1913. 
The summer plankton of the Gulf of Maine was of the same general 
type in 1913 as in 1912 (1914a). The lists of copepods, far the most 
important constituent of the macroplankton, are practically the same 
for the two years, the most numerous and most regularly occurring 
species was Calanus finmarchicus. But Calanus hyperboreus, taken 
only once in 1912 occurred at four stations in 1913, once in large 
numbers (p. 286); Eucheata norvegica was, likewise, taken more 
regularly in 1913, where it was practically universal in the deep waters 
of the Gulf (fourteen stations) than in 1912 (nine stations); and 
Metridia longa is recorded for the first time from our waters. Anoma- 
locera was taken more regularly in 1913 than in 1912, but in this case 
the difference is probably apparent rather than real, due to different 
types of nets used on the surface, where Anomalocera is most abun- 
dant. LHuchirella rostrata, singularly enough, was taken twice in each 
year, once on each side of the Gulf. 
In the case of the hyperiids the difference between the hauls of the 
two years was much greater, because Huthemisto bispinosa, a species 
common in the centre of the Gulf in 1913 was not found at all during 
the preceding summer. Its history during the year in Massachusetts 
Bay is as follows: — absent there during the summer of 1912, it must 
have appeared in the early autumn, for it was about half as numer- 
ous as compressa in November (1914b). But later in the season it 
was proportionately rare in the hauls (six compressa to one bispinosa 
in April) and by August, 1913, the Euthemisto component of the 
plankton of Massachusetts Bay was once more exclusively compressa. 
| This local series of changes suggests the possibility that there may be a 
parallel series for the Gulf as a whole, bispinosa appearing seasonally, 
| in winter and spring, to disappear again in summer. If this be the 
case, the species must have persisted longer in 1913 than it did in 1912. 
| But the appearance of bispinosa may have been the result of an inva- 
sion of the Gulf by this species during the autumn of 1912. In both 
summers HLuthemisto compressa was very generally distributed over the 
/Gulf. Parathemisto oblivia, taken at two Stations (10032 and 10036) 
in 1912, was not detected at all in the hauls of 1913. The rarity of 
! this species is interesting because of its wide distribution and frequent 
occurrence on the other side of the Atlantic (p. 341). The remaining 
‘hyperiids, Hyperia galba, H. medusarum and Hyperoche were occa- 
sionally represented in both years. 
The only pteropod which we have found in any great numbers in the 
t 
