[439] INVERTEBRATE ANIMALS OF VINEYARD SOUND, ETC. 145 
of Cancer irroratus, (p. 312, Plate VIII, figs. 37, 37a,) and of Platy- 
onichus in the zoéa and megalops stages, were taken in vast numbers, 
especially in bright sunshine, together with similar larvw of many 
other species. The larve and young of the lobster (Plate IX, figs. 38, 
39) were also abundant in mid-summer. The numerous specimens ob- 
tained have enabled Mr. 8. I. Smith to describe the interesting meta- 
morphoses of our lobster, which were entirely unknown before. The 
young swim actively at the surface, like a shrimp, until more than half 
an inch long. The larvee and young of the various species of shrimps 
are also abundant. The curious larvie of Squilla empusa (Plate VIII, 
fig. 36) were often met with. 
Several species of Amphipods are also common at the surface. The 
most abundant were Calliopius leviusculus, of which Mr. V. N. Edwards 
also took numerous large specimens in February and March; Gammarus 
natator, Which was usually common, and occurred in immense numbers 
August 10 and on several other occasions; and a Hyperia, which infests 
several species of large jelly-fishes, and also swims free, at will. The 
Phronima is a related genus, but is very remarkable for its extreme 
transparency, which renders it almost invisible in water. Jdotea irro- 
rata (p. 316, Plate V, fig. 23) and I. robusta, Plate V, fig. 24) were 
very common among masses of floating eel-grass and sea-weeds, and 
the latter was also very often found swimming entirely free. 
A species of Sapphirina (Plate VII, fig. 33) was found in great num- 
bers among Salpa, off Gay Head, on several occasions, early in Septem- 
ber. This is one of the most brilliant creatures inhabiting the sea. It 
reflects the most gorgeous colors, blue, red, purple, and green, like fire- 
opal, although when seen in some positions, by transmitted light, it 
is colorless and almost transparent. Under the microscope, when 
living, it is a splendid object, whether seen by transmitted or reflected 
light, the colors constantly changing, as it is turned in different posi- 
tions. When seen beneath the surface of the sea, in large numbers, 
the appearance is very singular, for each one as it turns in the right po- 
sition reflects a bright gleam of light, of some brilliant color, and then 
immediately becomes invisible, and these scintillations come from dif- 
ferent directions and various depths, many of them being much farther 
beneath the surface than any less brilliant object could be seen. In 
some cases one or more were found in the branchial cavity of Salpe, 
but whether this is normal or accidental was not determined. 
The species of Argulus are parasitic on the exterior of fishes, but we 
found at least three species swimming free at the surface. It is, there- 
fore, probable that they are able to leave their hosts for a time, and 
thus to migrate from one fish to another. The species of Caligus are also 
parasites on fishes, to which they firmly adhere, but the half-grown 
young of one species was taken at the surface in the towing-nets. 
Numerous species of Annelids, in the larval and young stages, were 
taken at the surface, but many of them have not yet been identified, 
