400 



MEDUSA OF THE WORLD. 



respects and were evidently Aglaura hemistoma, the average length of the peduncle being about 

 equal to that of the bell-radius. 



A curious aberration, shown in text-figure 251, was abundant at Naples, Italy, during the 

 winter of 1 907-1908. In nearly every medusa seen during the winter two or more of the gonads 

 were fused laterally. In some cases all 8 gonads were thus fused, forming an umbrella-like 

 expansion around the peduncle. Among thousands of specimens of this medusa from Tor- 

 tugas, Florida, I have never seen an aberration of this sort. 



Aglaura hemistoma var. "nausicaa." 



Aglaura nausicaa, Haeckel, 1879, Syst. der Mcduscn, p. 274, taf. 16, fig. 1. 



( ?) Aglaura vilrea, Fewkfs, 1882, Bull. Mus. Comp. Zool. at Harvard College, vol. 9, No. 7, p. 277, plate 7, fig. 10. 

 Aglaura hemistoma, var. Nausicaa, Maas, 1893, Ergeb. der Plankton Exped., Bd. 2, K. c, p. 26— Mayer, 1900, Bull. Mus. 

 Comp. Zool. at Harvard College, vol. 37, p. 65. 



Distinguished from the typical Aglaura hemistoma by the following characters: The bell 

 is egg-shaped, having a rounded contour, and the peduncle is extremely short, being only about 

 one-tenth as long as the stomach. The animal is colorless and transparent. Haeckel found this 



form in 1877 in the Mediterranean, and the Plankton 

 expedition of 1889 captured it in the Sargasso Sea and 

 also south of the Cape Verde Islands. Young, some- 

 what contracted, specimens of Aglaura hemistoma present 

 the appearance of A. nausicaa. 



Aglaura hemistoma var "prismatica" Maas. 



Lessonia radiata ( ?), Eydoux et Souleyet, 1841-52, Voyage de la Bonite, 

 tome 2, p. 643, Zoophytes, plate 2, fig. 16. 



Aglaura prismaiica,M\f,s, 1897, Mem. Mus. Comp. Zool. at Harvard College, 

 vol. 23, No. t,p. 24, plate 3, figs. 4, 5. — Acassiz, A., and Mayer, 1899, 

 Bull. Mus. Comp. Zool. at Harvard College, vol. 32, p. 165.— Maas, 

 1905, Craspedot. Medusen Sibogz Expedition, Monog. 10, p. 58; 190ft, 

 Revue Suisse de Zool., tome 14, p. 97, plate 3, fig. 12. 



Bell about 3 to 4 mm. in height and about as broad 

 as high; the walls, although rigid, are exceedingly thin; 

 the side-walls of the bell are vertical, the top quite flat, but 

 with a slight apical projection. There are about 60 ten- 

 tacles, so fragile that they were broken off" short in every 

 specimen observed by us. 8 club-shaped lithocysts about 

 midway between the 8 radial-canals; each lithocyst con- 

 tains a single concretion. Velum very large and powerful 

 and it is chiefly by means of its rapid movements that the medusa is enabled to dart through 

 the water. The 8 radial tubes are straight and very narrow. Manubrium flask-shaped, 

 half as long as depth of bell-cavity including the peduncle. 4 prominent cruciform lips. 

 The 8 sausage-shaped gonads project outward from the sides of peduncle at the point of junc- 

 ture of the 8 radial tubes with stomach. Gonads and entoderm of stomach usually brownish- 

 red in color, but some specimens are nearly transparent. 



Widely distributed over the tropical Pacific, Aglaura "radiata" Haeckel is probably only 

 a contracted specimen of A. prismatica. I concur with Bigelow, 1909, in the opinion that 

 this so-called "variety" can not be distinguished from Aglaura hemistoma. 



Aglaura hemistoma var "laterna" Maas. 



Aglaura laterna, Haeckel, 1879, Syst. der Medusen, p. 274, taf. 16, fig. 2. 



Aglaura hemistoma var. laterna, M*as, 1893, Ergeb. der PlanUton Exped., Bd. 2, K.C., p. 25, taf. I, fig. 14. 



The bell is 8 mm. in height and 6 mm. in diameter; due to contraction its lower part 

 is an 8-sided prism, while the upper part has the shape of an 8-sided frustum of a pyramid; 

 bell-walls extremely thin. 16 to 32 tentacles, about as long as bell-height, terminating in club- 

 shaped, swollen ends. 8 lithocysts midway between the 8 radial-canals. Velum large, provided 

 with powerful muscles. Peduncle trumpet-shaped, long, and slender, about half as long as 

 bell-height and twice as long as stomach. Stomach spindle-shaped, with four upwardly 



Fig. 252. — Aglaura "nausicaa," after Haeckel, 

 in Das Syst. der Medusen. 



