466 MEDUSAE OF THE WORLD. 



cular system of Geryonia more than fifty years ago, the life-history of the parasitic Cunoc- 

 t ant ha is not yet completely known. The latest studies are those of Woltereck, 1905, who 

 found numerous amoeboid cells in the gallert of a young Geryonia. Some of these cells had one, 

 others 2, 3, or more nuclei, and it is probable that the amoeboid cells with 2 nuclei have resulted 

 from the fusion of two mononuclear cells, but no such process has been actually observed in 

 C. parasitica. In Cunina probosciJea, however, according to Metschnikoff, amoeboid germ- 

 cells wander out from both the male and female gonads, and after dividing for a time in the 

 entodermal canals and gallert of the medusa they finally fuse in pairs, one cell engulfing the 

 other of each pair. It seems possible, therefore, that a similar fusion takes place in the free 

 germ-cells of Cunoctantha parasitica. However this may be, when the amoeboid cells have 3 

 nuclei, it is seen that one is larger than the other two, and this difference becomes much 

 greater when there are 4 and more nuclei. 



The cell with the large nucleus grows rapidly and sends out pseudopodia into the gelat- 

 inous substance of the Geryonia. Meanwhile the small nuclei within this giant-cell have 

 greatly increased in number and cell-walls arise between them so that the giant-cell contains 

 within itself a cup-shaped cluster of small cells, each with a single nucleus. 



This cup-shaped mass of cells then migrates to the surface of the still-enlarging giant nurse- 

 cell and soon breaks through and forms a raspberry-like cap of cells upon one side of the giant- 

 cell. The outer surface of the raspberry-shaped mass becomes ciliated. At first the cap is 

 composed of a single layer of cells, but soon it becomes 2-layered and the outer layer becomes 

 the ectoderm and the inner the entoderm of the larval Cunoctantha. 8 tentacles appear simul- 

 taneously around the sides of the cap-like larva. The 2-layered cap grows so as to inclose much 

 of the giant nurse-cell, which still persists undivided and with only one nucleus, even after the 

 larva begins to give rise to medusa-buds. 



The later stages have been studied by Metschnikoff and Maas. The 2-layered larva 

 elongates and gives rise to numerous medusa-buds upon its sides. Each medusa-bud is at 

 first a simple evagination of both ectoderm and entoderm of the larva. The mouth breaks 

 through before the lappets or tentacles develop. The 8 tentacles and 8 lappets develop simul- 

 taneously, both being outgrowths from the stomach-wall of the bud. The bell-margin has 

 8 lappets from the first and the tentacles do not change their position. The gelatinous sub- 

 stance is a product of the entoderm. There is no peripheral canal-system at any stage. The 8 

 radial stomach-pouches are formed through the flattening of the primitively polyp-shaped 

 buds. It is evident that the medusae arise as asexual buds, hence through an alternation of 

 generations, from the stolon-like larva. 



The young medusas escape into the water, apparently, through the mouth of the Geryonia. 

 When set free, the Cunoctantha has 8 marginal lappets alternating with 8 tentacles, which are 

 about as long as the bell-radius. There are also 8 marginal sense-clubs, each with 2 small 

 concretions. The otoporpae above the sense-clubs develop after the clubs have appeared. 



Cunoctantha fowled Browne. 

 Cunoctantha fowteri, Brownf, 1906, Trans. Linnean Soc. London, scr. 2, Zool., vol. 10, pp. 164, 177, plate 13, figs. I, 2. 



Bell 4 mm. wide, watch-glass-shaped, about 3 times as broad as high. 8 tapering ten- 

 tacles, about equal in length to diameter of umbrella. The 8 marginal lobes have rounded 

 outlines, with 5 sensory-clubs upon each of the lobes. There is a long, narrow line of nemato- 

 cysts forming an otoporpa over the exumbrella above each sensory-club. Peronial furrows 

 broad and shallow. Velum not present in the single specimen found. Mouth wide and circular 

 when expanded, the central stomach flat and lenticular and less than half as wide as bell- 

 diameter. The 8 radial stomach-pouches are quite narrow and the intertentacular spaces 

 between them are wide. Each stomach-pouch is widest at its middle and is spindle-shaped in 

 outline, being quite narrow where it arises from the stomach and also at its distal end. The 

 pouches are not cleft at their distal ends by the insertions of the tentacles, for the roots of the 

 tentacles lie above them as in other species of Cunoctantha. 



The most remarkable characteristic of this medusa is the presence of medusa-buds in 

 various stages of development upon the 8 peripheral stomach-pouches. These buds are not 

 parasites, but are formed from both ectoderm and entoderm of the stomach-pouches and 



