216 BULLETIN OF THE 



to say that Nanomia is no less graceful than the beautiful " sea necklace," 

 Agalma, iu all the motions of tentacles and tentaculai" knobs. 



Axis. — The axis of Nanomia is long, highly flexible, muscular, dotted with 

 reddish pigment spots. It is divided into two regions, which may be known 

 as the nectostem (ns) and the polyp-stem (ps). The length of the latter 

 is several times that of the former. The polyp-stem appears to be more easily 

 bent than the nectostem, but this appearance is brought about by the rigidity 

 imparted to the latter by the close approximation and form of the nectocalyces. 

 It is needless to say that the axis, as in all Physophores, is hollow throughout, 

 and that from it most of the appendages ot the colony have arisen. 



Float. — The float (/) resembles that of other Physophores. It is a small 

 sac enclosed in an enlargement of the axis, and has reddish pigment in its 

 outer walls. The contents seem to be a bubble of air or gas, as in other 

 Siphonophores. The longer axis of the float does not coincide with that of 

 the axis of the Nanomia, but is bent at a small angle. 



Nectocalyces. — The nectocalyces (no) are biserial in their arrangement, 

 with bell openings pointing in opposite directions. Their close approximation 

 imparts to the stem (nectostem) a rigid character, which however disappears 

 when their connection with it is once broken. The rows of nectocalyces are 

 transparent, gelatinous, almost invisible as the animal swims in the water. 

 Near the float there is a small cluster of undeveloped bells, the full grown 

 being more distant from the float than the less developed. The specimen 

 figured has thirteen pairs of well developed nectocalyces. Each nectocalyx is 

 bell-shaped, fastened to the axis at the apex, and has two lateral horns or 

 spurs, shown in the figure in profile, which interlock with corresponding spurs 

 from the opposite side of the axis. 



The structure of the bell and its tubes is well described by A. Agassiz. 

 The bell is rounded, with small circular orifice, slightly closed by a thin 

 velum. The bell cavity is spacious. The chynjiferous tubes are four in num- 

 ber, in addition to a marginal vessel and a single tube communicating, through 

 the point of union of the bell and stem, with the cavity of the axis of the 

 animal. 



The fact that the nectocalyx is slightly flattened on the upper and lower 

 sides, and the existence of a corresponding bulge on the remaining sides has 

 brought it about that, while the radial tubes of the nectocalyx of the former 

 spheromeres is regular and straight, passing from common junction directly to 

 bell rim, those of the two lateral spheromeres are tortuous, forming a single 

 loop, as shown in the figure (Plate III. Fig. 2). This character is by no means 

 peculiar to Nanomia, but is an interesting fact in the asymmetrical develop- 

 ment of the bell. 



ffydrophyllia. — The bracts, covering scales, or hydrophyllia (hph) are 

 colorless, transparent bodies, covering the bases of the appendages to the 

 polyp-stem. Each hydrophyllium is irregularly rectangular to triangular in 

 shape. Two adjacent sides of the rectangle are so elongated that a triangular 



