SEMAEOSTOME.E — DESMONEMA, CYANEA. 



595 



The medusa appears to be common from Decemlier to June in the Antarctic reijion, and 

 is reported from both sides of the Straits of Mai;elian, Kerguclcn, and the Falkland Islands; 

 and from Kaiser \\ilhelm Coast, South Victoria and Alexander I Land along the ice-edge 

 of the Antarctic continent. 



Ephyrae 3 to 10 mm. wide are found in January and February, and Vanhoffcn records a 

 young medusa in the Mi-dora stage from Causs Station, Kaiser Wilhelm Land on April 14. 

 This medusa was 38 mm. m diameter, the mouth-arms 16 mm. long. There were 8 principal 

 tentacles about two-thirds as long as bell-diameter, and 4 of these were bordered on one side 

 by a small tentacle oi recent development, figure 379. The lips and gastric cirri were 

 brownish-red, other parts being translucent milky-blue. A later stage is described b\' Browne 

 (see figure l,j'^)- 



Genus CYANEA P^ron and Lesueur, 1809. 



Cyanee2, Peron and Lesueur, 1809, .Ann. Mus. Hi^r. Nat. Paris, tome 14, p. 363. — Kschscholtz, 1829, Svst. dcr Acaleplien, 

 p. 67. — Lf.sson, 1843, Hist. Zooph. Acal., p. 379.— Brandt, 1S38, Mrm. Acad. .Sci. St. Petersbourg, Sci. Nat., sit. 6. tome 

 4, p. 77. — Forbes, 1848, British Naked-Eyed .Med usee, p. 77. — Agassiz, L., 1S62, Cont. Nat. Hist. U. S., vol. 4, pp. 11 <;, 

 161. — Agassiz, A., 1 865, North Amer..Acal., p. 44. — voN Lendenfeld, 1882, Zeit. fiir wissen. Zool., Bd. 37, p. 465; 1884, 

 Proc.Linnean .Soc.New .South Wales, vol. 9, p. 275. — Bigelow, R. P., 1900, Mem. Boston Soc. Nat. Hist., vol. 5, p. 21 1 . — 

 Hargitt, C. W., 1902, American Naturalist, vol. 36, p. 555. — M.vas, 1904, Result. Camp. Sci. Prince de Monaco, fasc. 28, 

 p. 5^; 1906, Fauna .Arctica, Bd. 4, Lfg. 3, pp. 486, 505; 1903, Scyphomedusen der Siboga Expedition, Monog. 11, p. 28. — 

 Vanhoffen, 1906. Nordisches Plankton, Nr. 11, p. 51. 



Proc\aTieii+ Meilorti-^ Stenopf\clui+ DesmoTienia (in part)+ Cvanca, Haeckel, 1880, Syst. der Medusen, pp. 524-528. 



The type species is C. capdhita of the North Atlantic, Pacific, and Arctic Oceans, 

 the largest of all known medusae. 



It 



GENERIC CHARACTERS. 



Cyaneidae with 8 marginal sense- 

 organs and with 8 adradial crescentic 

 groups of tentacles. Each group consists 

 of several rows of tentacles. With radial 

 muscle strands in the subumhrella. 



When young only 8 simple tentacles 

 arise in the adradial clefts between the 

 ephyra lobes, but later the margin grows 

 beyond them, leaving them to project from 

 the floor of the subumhrella. In the mean- 

 time the tentacles increase in number, 

 becoming a row in each adradius, but 

 finally they come to lie in two or more 

 rows. Haeckel has constituted a special 

 genus for each of these growth-stages. 

 He calls the 8-tentacled stage" Procyanea." 

 The stage with 24 tentacles, 3 in each 

 adradius, he names " MeJora," and when 

 there are 5 tentacles in each rowthe medusa 

 becomes a " Stenoptycha" ; then as long as 

 the medusa remains with the tentacles of 

 each cluster in a single row it is a " Des- 

 monema" and finally when older and the 

 tentacles begin to develop in two or more 

 rows in each cluster the medusa is called a 

 Cvanea. It is possible that some medusae 

 Detmonema chierchiana. mav become mature in, and never advance 



Fig. 378.— .After Browne, in Trans. Royal. Soc. Edinburgh. beyond, Haeckel's " Dismoiicma Stage," 



Fig. 379.— Young medusa, after Vanhoffen in deutsch. Sudpolar but it is Certain that Others paSS through this 

 Expedition. ,. • j 1 ^ /^ 



condition and become mature as L\anea. 

 Medusae of Cyanca are abundant in the .Arctic and Antarctic, but are not found in the 

 tropics. Being dependent upon a fixed scyphostoma-stage for development, they are confined 

 to the proximity of coasts where the water is relatively shallow. 



