MUSEUM OF COMPARATIVE ZOOLOGY. 2G5 



take origin from the base of the polypite, near its union with the peduncle. 

 The axis is hxrge, muscular, and spirally coiled.* The color of its wall is yellow 

 and orange. The Hoat is in no respects peculiar, and bears around the o[)ening 

 by which the air-sac communicates with the surrounding water a number of 

 regularly arranged pigment-spots. The nectocalyces are arranged in manj'- 

 rows, opening laterally in spirals on all sides of the animal. The most distally 

 placed bells from the float are the oldest, as in other Physophores. Directly 

 under the float there is a small cluster («) of undeveloped swimming-bells. 

 Each nectocalyx has a cubical form, the Hat faces of which conform to the 

 surfaces of adjoining bells. The bell has in other particulars a great resem- 

 blance to the nectocalyx of other Physophores, and does not seem to dili'er 

 from that of ForsJcalia contnrta. The course of the radial tulies is like that in 

 Aijalmn. At the union of the radial tube with the ring canal on the liell 

 margin, there is a large yellow spot, which is an ocellus or sense organ (if tlie 

 same kind as similar bodies in certain hydroid medusa}. On either side of it, 

 there is a short papilla of imknown function. In the undeveloped nectocalyx 

 we find a single large yellow spot of this kind, which forms a very conspicuous 

 body on the bell margin. Later in the growth of the nectocalyx, its compara- 

 tively large size diminishes. We should expect, if anywhere among the Physo- 

 phores, a development of the sense oi'gans in Stephanomia. Its motion through 

 the water is so rapid that organs of this kind are necessary. Ocelli on the margin 

 of tlie nectocalyx are, however, not peculiar to Stephanomia. In our common 

 Diphycs similar ocelli are found, three in number, on the margin of the anterior 

 nectocalyx. The attachment of the covering-scales to the base of the polypites 

 and the distal end of the peduncle imparts to the polyx stem of Siephanomia 

 a diameter relatively greater than that of other Physophores. In Agulma the 

 covering-scales spring from the base of the polypite, of which the peduncle is 

 very short. In Stcpihanomia, however, the pedicle, which bears the feeding- 

 polyp, is so long that the covering-scale seems to hang Irom a point midway 

 between the axis of the animal and the mouth of the polypite. The tastern do 

 not differ from the tastern of other Physophores, except that they have long 

 peduncles, as is the case also with the polypites. 



The male and female bells arise from the same tastern at their junction with 

 their peduncles. The colony is monoecious. The sexual bells resemble closely 

 those of Agalmopsis (jracile, sp. nov. In its motion through the water it is one 

 of the most active of all the Physophores. The combination of so many series 

 of nectocalyces can pi-opel it in almost any direction with the greatest ease, 

 whereas in Agalma and some others these propelling organs are obviously 

 placed in a disadvantageous position for quick movement. As it passes 

 through the water in the line of its axis, it sometimes combines a rotation of 

 the stem with the direct forward motion. 



When the cohmy is quiet in the water the peduncles of the polypites and the 

 organs which they bear are widely extended, so that its diameter is very great 

 as compared with its length. As the colony begins to advance in the line of 

 * In the same way as For.skalia contorta. 



