44 CCELENTERATA AND 



every summer in Narragansett Bay. The Physophora 

 larva is the most common. 



The primitive larva consists of a primitive polypite 

 formed directly from the egg or budded from its side, a 

 helmet-shaped covering-scale, the primitive covering-scale, 

 or hydro phy Ilium, through which pass an unbranchal prim- 

 itive canal and an embryonic tentacle with transitory 

 tentacular knobs. The primitive larva swims at moderate 

 depths in the aquarium. 



The Athorybia stage has no primitive covering-scale, 

 but a circle of serrated, provisional covering-scales, a 

 transitory tentacle with tentacular knobs, afloat, polypite, 

 taster, and is destitute of nectocalyces. The axis from 

 which the circle of serrated covering-scales in this larva 

 arises is also probably transitory. The Athorybia stage is 

 generally found free on the surface of the water. 



The Physophora larva resembles closely the adult with 

 the exception that it still retains the embryonic tentacle 

 with its characteristic tentacular-knobs. Float and necto- 

 calyces like those of the adult. The portion of the stem 

 below the nectocalyces, called the polypstem, is enlarged 

 at its very extremity somewhat as in the genus Physo- 

 phora. Covering-scales like those of the adult are present, 

 and the permanent tentacle with the knob characteristic of 

 the adult coexist with the embryonic. Both depend from 

 the extremity of the stem opposite the float. A small 

 cluster of immature buds just below the lower pair of nec- 

 tocalyces are undeveloped polypites and tasters. 



PJiysalia. The youngest Physalia has a float and poly- 

 pite with a single tentacle. Of the very young Physalia 

 little is known. There are no known provisional organs. 

 The float is small, spherical or slightly oval in form. 



The young stages of Diphyes have never been observed 

 in Narragansett Bay, yet certain forms called the Diphy- 



