600 



MEDUSAE OF THE WORLD. 



later stages the young medusa develops an increasing number of tentacles and the lips form 

 long curtain-like folds surrounding the 4-cornered mouth. When the young medusa is about 

 7 mm. in diameter there are a number of slender papillae upon the exumbrella and these are 

 clustered especially at the aboral apex. In this stage the medusa rarely comes to the surface, 

 but frequently spreads its oral fringes out over the bottom or sides of the aquarium and 

 remains sedentary. The same habit is exhibited by the closely allied " Cyanea fnlva" which 

 is represented in figs. I to 7, plate 66, and figs. I to 3, plate 67; and it is probably due to 

 some such habit that the young are rarely to be found upon the surface while the large and 

 mature medusae are very abundant. The scyphostoma and young medusa feed upon pro- 

 tozoa, starfish, and mollusk larvae. 



Macallum, 1903, studied the composition of the body-juices of Cyanea arctica and found 

 them to be as follows: 



The SO 3 is less in Cyanea than in sea-water by about 32 to 36 per cent and the medusa 

 contains more iron and less iodine than does sea-water. 



M'Kendrick, 1881, studied the chemical composition of the coloring matter of Cyanea 

 and found that the blue pigment of Cyanea and Aurellia is in the form of granules surrounded 

 by clear protoplasm. This pigment is soluble in acids, but is precipitated in neutral or acid 

 solutions. Hence when the medusa becomes acid through decomposition after death the pig- 

 ment dissolves out into the water, but during life it remains stable. This pigment matter of 

 Cyanea shows two absorption bands in the spectrum, one in the red and one in the orange, 

 very much as in Stentor cixruleits. 



Holt, 1902, finds that in the North Sea this medusa is accompanied by young whiting. 



Cyanea capillata var. fulva, L. Agassiz. 



Plate 66, figs, i to 7; plate 67, figs, i to 3. 

 Cyanea fulva, Agassiz, L., 1862, Cont. Nat. Hist. U. S., vol. 4, pp. 119, 162. Agassiz, A., 1865, North Amer. Acal., p. 46. 



This southern variety is distinguished from the northern C. arctica by the light yellow or 

 yellow-brown color of the entoderm of its gastrovascular system, which is never rich brown, 

 as in the northern C. arctica. It is also much smaller, being rarely over 200 mm. in diameter. 

 The lappet notches are more uniform than in C. arctica and the tentacles are much less numer- 

 ous. The oral fringes, also, are less voluminous and by no means so complexly folded as 

 in C. arctica. This variety appears in great numbers early in May on the southern coast 

 of New England, and the medusae arrive at maturity about the middle of June, after which 

 they suddenly disappear. We have, however, met with swarms of them about 20 miles off 

 Barnegat Bay, New Jersey, early in August. This variety has not been taken north of Cape 

 Cod. The development is similar to that of the closely allied C. arctica. 



We may regard this as a local race of C. arctica, which ranges from Cape Cod, Massa- 

 chusetts, southward to the Carolmas; where it is replaced by a still more southerly variety, 

 C. arctica var. versicolor. 



Cyanea capillata var. versicolor L. Agassiz. 



Plate 65, figs. I and 2. 

 Cyanea vcrsicolar, Agassiz, L., 1862, Cont. Nat. Hist. U. S., vol. 4, pp. 119, 162. Agassiz, A., 1865, North Amer. Acal., p. 46. 



This form bears the same relation to Cyanea arctica var. fulva as fulva does to the northern 

 C. arctica. It is smaller than fulva, but is distinguished especially by its pink coloration. 

 Mature medusae are about 1 10 mm. in diameter and are found in swarms off the coast between 

 Cape Hatteras, North Carolina, and Cape Canaveral, Florida. They are practically confined 

 to pure open water and do not frequent the harbors. The mature medusae bear many ball- 



