PLANKTON OF THE GULF OF MAINE 
163 
Large ones, however, especially the females with eggs, have rarely been taken in 
our surface nets; and even medium-sized individuals have usually been but sparsely 
represented in the surface hauls, although we have occasionally met exceptions to 
this rule, notably in the northeastern part of the gulf during August in 1912 and 
1913 (stations 10032 and 10096) and off Marthas Vineyard on July 10, 1913 (station 
10062). On the other hand, E. compressa, like Calanus, has usually proved more 
abundant above than below 100 meters depth whenever two or more subsurface hauls 
have been made at different levels. 
The bathymetric distribution of the larvae of Euthemisto differs from that of 
the adults, for they are usually most numerous at or close to the surface. The 
fact that we have taken them in swarms in the surface nets at several stations where 
their parents (or at least females -with eggs) were plentiful at deeper levels is evidence 
that they rise through the water immediately after they are hatched — one of the 
innumerable provisions of nature for the perpetuation of the species, for otherwise 
they would inevitably be devoured by their own voracious progenitors (p. 107). 
Examples of a bathymetric stratification of this sort as between adults and larvae 
were noted in the eastern part of the gulf (stations 10092 and 10093) and off Marthas 
Vineyard (station 10112) in August, 1913; over Georges Bank in July, 1914 (sta- 
tions 10215 and 10219); off Shelburne in June; in the western basin in August, 
1915 (stations 10293 and 10307); and off Marthas Vineyard in July, 1916 (station 
10353). 
Both species of Euthemisto — compressa and bispinosa — like Calanus jinmarchicus 
and Sagitta elegans, tolerate very wide fluctuations of temperature and salinity, as, 
indeed, they do in European waters as well (Tesch, 1911). So far as actual occur- 
rence goes, we have taken them over the whole range of temperature prevailing 
within the limits of the gulf, from the icy waters of winter and of the Nova 
Scotian current, on the one hand, to the summer-heated surface of the western 
basin and the warm waters along the outer edge of the offshore banks, on the other; 
likewise over the entire range of salinity proper to the open waters of the gulf, except 
for the very lowest. It is not possible to draw any close parallel between the abund- 
ance (or reverse) of Euthemisto and the temperature from the data so far obtained, 
but we have never found it abundant in the coldest season, and most of the rich 
catches have been made in temperatures warmer than 5°, as appears from the follow- 
ing list of the readings at and above the levels at which the horizontal parts of the 
hauls were made, at several stations productive in large Euthemisto. 
General locality 
Station 
Date 
Depth in 
meters 
Temper- 
ature in 
degrees 
Eastern basin... 
10092 
Aug. 11,1913 
Aug. 31,1915 
July 25,1914 
Aug. 11,1914 
June 24, 1915 
170 
5+ 
Western basin ... .... ... 
10307 
40 
7-8+ 
Off Cape Sable 
10229 
80 
5-6+ 
Do 
10243 
40 
7. 5+ 
3+ 
Browns Bank 
10296 
50 
Do 
10228 
July 24,1914 
___do 
0) 
60 
14. 72 
Do... 
10228 
8. 3+ 
12+ 
Georges Bank .. . 
10216 
July 20, 1914 
July 21, 1914 
Aug. 25,1914 
July 24,1916 
July 27,1914 
50 
Do 
10219 
40 
13+ 
Off Marthas Vineyard 
10258 
25 
12+ 
Do 
10351 
160 
4.8+ 
Oil Shelburne, Nova Scotia 
10231 
(<) 
6. 62 
1 Surface. 
