406 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
Coscinosira polychorda, Thalassiothrix nitzschioides, and Rhizosolenva 
semispina. 
It is interesting to note that the diatom swarm was not uniformly 
distributed. On the contrary, while the net was towing near the 
surface, we could see it pass through clear bands, as well as through — | 
bands of diatoms, which gave it a brown color. This observation 
shows, too, how erroneous an idea of the quantitative richness of | 
diatoms in the waters of Massachusetts Bay would have been afforded — 
by a single vertical haul with a quantitative net. 
At this same station the zodplankton was as poor as the diatom 
plankton was rich, the only large organisms yielded by the nets being 
a few dozen copepods, one Euthemisto, two Clione lumacina and a few 
unrecognizable bells of some agalmid siphonophore, besides a few 
barnacle (Balanus) nauplii, and, to my surprise, a considerable num- 
ber of tests of Foraminifera. This was the first haul in which there 
were no Sagittae. 
The diatom swarm continued at its height during the first half of 
April, hauls on the 14th (St. 10,056) yielding the same rich Thalas- 
siosira plankton just described, and the zodplankton still proved to be 
very scanty, the catch being only a few Calanus, one Tomopteris, one 
Sagitta elegans, one fragmentary Beroe, and one young Staurophora. 
But there were considerably more Balanus nauplii than before. 
No plankton hauls were made north of Cape Ann, except the one 
station in Ipswich Bay noted above, previous to March 29th. But 
from that date onward, Mr. Welsh’s stations show that the Thalassio- 
sira swarm filled the coast water very generally from Cape Ann to 
Cape Porpoise during the whole of April, often being so dense as to 
discolor the water. Thus on May 2, he writes “the water yesterday 
and today full of green slime,” and on the 3d, “the water is full of the 
greenish brown algae.” Microscopic examination of his catches 
showed that the plankton was extremely uniform qualitatively, con- 
sisting almost altogether of Thalassiosira, with an occasional specimen 
of the other species noted for Stations 10,055 and 10,056 (p. 405). 
The catches were very clean up to about the first of May, but about 
that date, they began to contain noticeable amounts of diatom debris, 
and as the season progressed the relative amounts of dead specimens, 
and variously fragmented remnants, grew progressively greater until 
by the 25th of the month there were very few living diatoms, con- 
trasted with large amounts of debris, among which the various genera 
which formed the swarm (particularly Chaetoceras and Thalassiosira) 
could be distinguished. In the latest hauls there were hardly any 
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