ETC. 451 



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 witb, and in small numbers, while the 

 Bolina alata, which is one of the most abundant species on the northern 

 coast of jSTew England, was not seen at all. The Aurelia flavidida 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 j)arents. Mr. A. Agassiz has, 

 however, recently ascertained that the young of a species of Udivardsia 

 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 hracMolata A. Aa.) 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 

 Edicardsia farinacea Y., of this coast, has but twelve tentacles when 

 adult, and U. elegans Y. 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 Polycystina would probably be found, if carefully 

 sought for, but we have not yet met with any of them. 



List of si)edes talcen at the surface of the ivater 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 j megalops j June, July, (438.) 



Callinectes hastatus, young, (438.) 



Many other species of Brachyurain the zoea and megalops stages. 



Hippa talpoida, young, 5 or 6""^ in length ; early in September, (339.) 



Eu[)agurus, several species in the larval stages ; July to September. 



Gebia alhnis, young, 4^^"^ long ; early in September. 



Homarus Americanus, larvine and young ; July, (395.) 



Crangon vulgaris, larvae and young ; June and July. 



