144 REPORT OF COMMISSIONER OF FISH AND FISHERIES. [438] 
In the general list of surface species only those that have been ac- 
tually observed are introduced, but it must be remembered that the 
greater part of the crustacea, annelids, mollusks, and echinoderms are 
well known to have free-swimming young, or larval forms, and that the 
list might easily be doubled by the introduction of such species, on 
theoretical grounds; but, by omitting them, the list serves to indicate 
how much yet remains to be done in this direction. There are large 
numbers of common species of which neither the young nor the eggs 
are known, and there are many others of which the eggs, or young, or 
both, are known, but the time required for the hatching of the eggs and 
the development of the young is not known. ‘The dates given in the 
lists refer only to the time of actual capture of the species, and it must 
not be inferred that at other seasons of the year any of the species so 
designated are not to be found; for, doubtless, many of those that swim 
free when adult may be found all the year round. And _ possibly 
some species may breed during every month of the year. But the 
breeding season of most species is probably of short duration, and 
therefore the larve and young may occur only at particular seasons. 
Mr. A. Agassiz has made a very large collection of the surface ani- 
mals in Vineyard Sound, Buzzard’s Bay, and off Newport, and to his 
labors we owe the knowledge of a large proportion of the jelly-fishes. 
He has also described the larvee and young of several Annelids and 
Nemerteans, and has described and beautifully illustrated the larvee 
and young of the common star-fishes, (Asterias,) and the green sea- 
urchin, (Strongylocentrotus Drébachiensis.) The Salpa Cabotti (Plate 
XXXII, figs. 254, 255) was also well described and illustrated by him ; 
and also other species, but a large part of the collection has not yet 
been elaborated. 
Our surface collections were made both in the day and evening, 
at various hours, chiefly by means of towing-nets and hand-nets. The 
evening or night hours are generally more productive than the day-time 
in this kind of collecting, but we were unable, owing to lack of time 
and superabundance of other specimens, to do as much night-collecting 
as we desired. 
Among the Crustacea there are a considerable number of species that 
swim at the surface when adult, and others till nearly half-grown, but 
the majority are free-swimmers only when quite young, or even only 
when in the zoéa and megalops stages, through which they seem, from 
Mr. 8. I. Smith’s observations on several of our species, to pass in a 
short time. The males of the common oyster-crab, Pinnotheres ostreum, 
(p. 367, Plate I, fig. 2,) were often caught in the day-time swimming at 
the surface in the middle of Vineyard Sound. The lady-crab, Platyon- 
ichus ocellatus, (p. 333,) of full size, was also occasionally caught swim- 
ming actively at the surface. The “ blue-crab,” or common edible 
crab, Callinectes hastatus, is well known to be an active swimmer, when 
adult, but most of those seen at the surface were young. The larve 
