32 



MEDUSAE OF THE WORLD. 



In the American form the development of nematocyst-rings upon the long tentacle is 

 subject to great variability. The Mediterranean S. cranoides Haeckel lacks such rings, 

 whereas they appear to be better developed in northern Atlantic specimens from the coasts 

 of Europe. The same difference appears to be exhibited by our American specimens, those 

 from Tortugas, Florida, being unnnged or only slightly ringed, while those from North Car- 

 olina are often profusely ringed. The apex of the bell often bristles with nematocysts, but 

 in some medusae it may be smooth. 



Browne, 1896 (pi. 16, fig. i), gives a figure of S. rubra derived from specimens found by 

 him at Valencia Island, off the Irish coast. He shows a narrow conical peduncle above the 

 stomach, the peduncle being about one-fifth as long as the gastric portion of the manubrium. 

 No such peduncle has been observed in the American S. " gracilis," when the bell is expanded, 

 although when it is somewhat contracted the appearance of a well-developed peduncle is 

 often produced. On the other hand, when the stomach is widely distended with food and the 

 bell expanded no peduncle may be seen. Haeckel's series of figures (taf. 2, figs. 10-12) will 



3> 



FIG. 4. Corymorpha nulans, after Hartlaub, in Nordisches Plankton. 

 (Young hydroids and mature medusa.) 



serve to illustrate the formation of a peduncle-like body of gelatinous substance above the 

 stomach through contraction of the bell. I have frequently seen the same phenomenon in 

 our American S. " gracilis" = S. cranoides Haeckel. I have also observed this peduncle in 

 living medusae of S. rubra taken off the coast of Cornwall, England. 



Hartlaub, 1907, gives a list of the bibliography and of localities for this species, and his 

 description of the medusa and the young hydroid are the best yet produced (see fig. 4). 



The egg is amoeboid as in Amalth&a. The young hydroid has a single circlet of 4 short, 

 knobbed, oral tentacles, and another circlet of 5 to 8 simple, flexible, filiform basal tentacles. 

 H. Miiller, 1908, finds that the full-grown eggs are very few in number, having developed at 

 the expense of other weaker egg-cells in the ovary, which they devour. The exoplasma is quite 

 wide and is separated from the germinal vesicle. The ooplasma is a network of delicate fibers 

 of wide mesh, and the exoplasma and endoplasma are distinct, one from another. The egg 

 contains numerous pseudo-cells in advanced stages of degeneration and also yolk-granules. 



