INVERTEBRATE ANIMALS OF VINEYARD SOUND, ETC. 439 



of Cancer irroratus, (p. 312, Plate VIII, figs. 37, 37a,) and of Platy- 

 onichus in the zoea and niegalops stages, were taken in vast numbers, 

 especially in bright sunshine, together with similar larva? of many 

 other species. The larvae and young of the lobster (Plate IX, figs. 38, 

 39) were also abundant in mid-summer. The numerous specimens ob- 

 tained have enabled Mr. S. I. Smith to describe the interesting meta- 

 morphoses of our lobster, which were entirely unknown before. The 

 young swim actively al the surface, like a shriurp, until more than half 

 an inch long. The larvae and young of the various species of shrimps 

 are also abundant. The curious larvae 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 heviusculus, 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. Idotea irro- 

 rata (p. 316, Plate V, fig. 23) and I. robusta, Plate V, fig. 21) 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 Sappliirina (Plate VII, fig. 33) was found in great num- 

 bers among Salpce, 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 Salpce, 

 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 Galigus 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 to wing-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, 



