Chap. V. THE GENUS POLYCLONIA. 



147 



the surflice of their base (PI. XIII'. Fig. 5). The marginal crenuhxtions of the disk 

 are, no doubt, also generic. The disk is very thin along the margin, but a little 

 further inward its thickness is suddenly increased, and that thickened i^ortion is so 

 furrowed as to assume a crenulate appearance {Figs. 6, 7, 8, 10, and 11). A com- 

 parison of our Polyclonia frondosa with the Polyclonia Mertensii of Brandt, leaves 

 no doubt that the species of the Gulf of Mexico differs from that of the Pacific 

 Ocean. Plate XXII. of Mertens shows that, in the species of Ualan, the lasso- 

 tentacles are of an enormous size, in comparison to those of our species, and are 

 more uniformly distributed upon the whole lower surface of the arms, to their very 

 tips, though the largest are about the centre, while in Polyclonia frondosa they are 

 chiefly clustered upon the base of the tentacles, and only a few of them are found 

 between their branching ramifications. The arms of Polyclonia Mertensii seem 

 also to be more slender, and longer than those of Polyclonia frondosa, and the 

 marginal crenulations of the first, more distinct and isolated than those of the 

 latter. The color of Polyclonia Mertensii is represented as a uniform yellowish brown, 

 the lasso-tentacles alone being white. Our species, on the contrary, has brighter 

 hues, the prevailing tint being a grayish blue, passing, sometimes, into olive color, 

 and sometimes into yellow, with lighter broad rays trending radiatingly in the 

 direction of the eyes. At some distance from the margin there is a broad circle 

 of a different tint, sometimes slightly marked, cat other times quite distinct, with 

 concentric bands of different tints, varying in different specimens from light gray 

 to bluish gray, or yellowish gray to paler or darker blue and purple. The whole 

 upper surface of the disk is adorned witli minute epidermal wrinkles or folds, radi- 

 atingly reticulate. 



Whether Polyclonia, contrary to what I have observed in Aurelia and Cyanea, 

 survives for a long time the period of breeding or not, I am unable to state from 

 direct observation; but this much is certain, that, while adult specimens of Poly- 

 clonia frondosa were found in the greatest abundance upon the reef of Florida, 

 I occasionally noticed, floating near the surface of the water, small Medusa?, varying 

 from a quarter to half an inch in diameter, which, owing to a general resemblance 

 to our Polyclonia, I was led to consider as the young of this species. They pre- 

 sented the same distribution of color, and the same unusual number of eyes, which 

 in itself distinguishes this genus from all the other Acalephs of the American coast. 

 There is, therefore, every probability that these young Medusa? were young Poly- 

 clonia?. But if this is truly the case, these young are highly instructive, as showing 

 the great resemblance there is between the Rhizostomea? and Semajostomea? in the 

 earlier periods of their growth; for, in the smallest of the young, the mouth was 

 wide open, as in the young Aurelia (PI. XP. Fig. 18), the \vhole oral apparatus 

 consisting in a broad funnel, with an entire margin, of a somewhat quadrangular 



