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[451] INVERTEBRATE ANIMALS OF VINEYARD SOUND, ETC. 157 
This species is capable of stinging the hands very severely if they be 
brought into contact with the hydroids attached to the lower surface of 
the floating air-bag. 
The Idyia roseola, so abundant on the coast of New England north of 
Cape Cod, was only occasionally met with, and in small numbers, while the 
Bolina alata, which is one of the most abundant species on the northern 
coast of New England, was not seen at all. The Aurelia flavidula is 
less common than north of Cape Cod, but was found in abundance in 
Buzzard’s Bay, in May, by V. N. Edwards. 
Many of the Polyps have free-swimming, ciliated embryos, but others, 
like many of the sea-anemones, are viviparous, discharging the young 
ones through the mouth. These young are of different sizes, and fur- 
nished with a small but variable number of tentacles, but in most 
other respects they are similar to their parents. Mr. A. Agassiz has, 
however, recently ascertained that the young of a species of Hdwardsia 
swims free in the water for a considerable period, or until it develops at 
least sixteen tentacles. In this condition it has been described as a dif- 
ferent genus and species, (Arachnactis brachiolata A. AG.) Whether the 
other species of this genus all have free-swimming young is still uncer- 
tain; if so, these young must differ considerably among themselves, for 
Edwardsia farinacea V., of this coast, has but twelve tentacles when 
adult, and ZH. elegans V. has but sixteen, while others have as many as 
forty-eight tentacles, when full grown. Among the Protozoa there are 
great numbers of free-swimming forms included among those commonly 
known as Ciliated Infusoria, but those of our coast have been studied 
but little. The germs of sponges also swim free in the water, by means 
of cilia. Species of Polyeystina would probably be found, if carefully 
sought for, but we have not yet met with any of them. 
List of species taken at the surface of the water on the southern coast of 
New England. 
In this list no attempt has been made to enumerate the numerous 
species of free Copepod Crustacea, which are very abundant, but have 
not been carefully studied. 
ARTICULATA. 
Crustacea. 
Pinnotheres ostreum, males and young, (438.) 
Cancer irroratus, in the zoea and megalops stages; June, July, (438.) 
Platyonichus ocellatus, young and adult; megalops; June, July, (438.) 
Callinectes hastatus, young, (438.) 
Many other species of Brachyura in the zoea and megalops stages. 
Hippa talpoida, young, 5 or 6™ in length; early in September, (339.) 
Eupagurus, several species in the larval stages ; July to September. 
Gebia affinis, young, 4™™ long ; early in September. 
Homarus Americanus, larvie and young; July, (395.) 
Crangon vulgaris, larve and young ; June and July. 
