PLANKTON OF THE GULF OF MAINE 
333 
Thanks to the confinement of Eukrohnia to considerable depths, where seasonal 
variations in the physical state of the water are slight, it is easy to establish the 
temperatures and salinities in which it most often occurs in the gulf, the former 
ranging from 1.3° to upward of 9°, the latter upward of 32.16 per mille, with most 
of the Eukrohnia living in water more saline than 32.5 per mille. Assuming 
Eukrohnia to occur close to the bottom, the maximum salinity in the gulf would be 
about 34.8 per mille. 
Our largest summer catches of this worm have been made in water of about 
6 to 8° temperature and of 33 to 34 per mille salinity, with an extreme range from 
about 5.9° to about 9.3° temperature and from about 32.6 per mille to about 35 
per mille salinity. In spring we have taken it in 1.3 to 6.7°. The seasonal data 
thus show that' Eukrohnia can survive in the gulf through a considerable range 
of temperature, from the coldest up to 9° or so, or even slightly warmer, and in 
water varying in salinity from slightly more than 32 to 35 per mille; that is, in all 
but the warmest and least saline locations. This is interesting, for with both the 
salinity and the temperature of the surface waters within these limits over most of 
the gulf in winter and spring, and with the water as cool and as saline as this only 
a few meters down even in midsummer, neither temperature nor salinity but probably 
ight is the factor that bars Eukrohnia from the upper layers of water at all seasons. 
With Eukrohnia occurring in the gulf only as an immigrant and not as a per- 
manent and endemic inhabitant, a few words as to its distribution in the waters to 
which the gulf is tributary will be germane. Originally supposed to be an Arctic 
animal, this glass worm is now known to be cosmopolitan in the high seas from Arctic 
to Antarctic; but except in high latitudes it is confined to waters so deep that it prob- 
ably never reaches the Gulf of Maine from the oceanic basin abreast of it. Hence, 
as Huntsman (1919, p. 476) points out, the Eukrohnia living in the upper 500 meters 
or so (and this includes practically all the representatives of the species collected 
either by the Gulf of Maine or by the Canadian fisheries expeditions) may be con- 
sidered as distinctly northern. It is known to be common in the cool, heavy, mixed 
water all along the continental slope from the Grand Banks of Newfoundland on 
the north to the latitude of Chesapeake Bay to the south (fig. 93) in depths of 300 
to 500 meters. For records of it east of Cape Sable see Huntsman (1919). How 
universal it is along this zone abreast the mouth of the Gulf of Maine and thence 
westward and southward in considerable depths will appear from the fact that it 
has been detected in the towings from 250 to 1,000 meters at 9 out of 12 Grampus 
and Albatross stations from 1913 to 1920, irrespective of the time of year (stations 
10076, 10220, 10233, 10352, 10368, 10384, 10393, 20044, and 20077). 
Outside the Gulf of Maine it is probably more numerous below 400 meters than 
above, for on February 22, 1920 (station 20044), none were found at 250-0 meters 
when a number were taken in a haul from 750-0 meters. Again, on the slope abreast 
of Cape Sable more Eukrohnia were taken in the haul from 800-0 meters on March 
19, 1920 (station 20077), than from 500-0; and on July 21, 1914, none were taken 
in a horizontal haul at 300 meters off the slope of Georges Bank at station 10218, 
but several were had at 400-0 meters at a neighboring station (10220) at about 
