82 BULLETIN OF THE 
swarms of Limacina, and of Sarsia and Aurelia? in the Bay of Kiel, and 
contrasts these swarms with the poverty of the surface of the sea far 
from land. We are scarcely justified in assigning the presence of food as 
the cause of the sudden appearance or disappearance of these swarms of 
pelagic animals, and we cannot entirely agree with Hensen when he as- 
serts that the Pyrosomz, Salpæ, and Ctenophoree occur in limited schools, 
depending upon the influence of the richer or poorer Plankton. A single 
day in a given locality is certainly not sufficient time to allow for such a 
change in the food supply of the sea as to account for the sudden appear- 
ance at sea or along our coasts of such masses of Salpæ, of Ctenophor:e, 
and of Diphyes as often render all attempts at surface or other pelagic 
fishing hopeless. 
It is true that in our experience we have frequently (in the open sea) 
passed over extensive tracts where the surface fishing was comparatively 
unproductive ; but we have rarely been twenty-four hours without 
finding some district which more than made up for the poverty of its 
neighborhood. 
HAECKEL’S PLANKTON STUDIES. 
In Haeckel's historical sketch of the study of the pelagic fauna,’ no 
well informed reader can fail to notice the absence of reference to most 
of the work done by Americans in this field. Surely, no investigator is 
justified in omitting from a general review of this kind the older litera- 
ture on the subject. We naturally suppose that no one willingly ignores 
the work of his predecessors, and, indeed, any one may be excused for 
not having at hand the latest pamphlet on a given subject. But there 
is no such valid excuse for disregarding contributions which date back 
ten or more years, and have been regularly noted in the annual reports 
of progress in zoölogy, in order to give undue prominence to publications 
which deal only indirectly with the subject in hand. 
If Hacckel had taken the pains to look up the literature of his subject, 
he would have found that there has been a vast amount of surface work 
accomplished by the American dredging expeditions, and that, while it 
is true that much of this material has not as yet been worked up, still 
it is not probable that any sea-coast has been so carefully explored as 
has the cast coast of the United States along its immediate shores, and 
along the course of the Gulf Stream, by the “ Fish-Hawk,” the “Blake,” 
1 Swarms of Aurelie, forming huge patches which discolor the surface of the 
sea over considerable areas are not uncommon in Massachusetts Bay. 
2 Plankton-Studien, von Ernst Haeckel, Jena, 1890. 
