ANTIKiMI.IM S.K MM.STKA. 



exumbrella, one above each of the 4 tentacle-bulbs. The throat of the medusa is blocked by 

 a spongy mass of entoderm. There is a cup-like depression in the center of the exumbrella. 



This medusa attaches itself by its suctorial mouth to the throat of the opisthobranch 

 mollusk, Phyllirhoe. It may lie derived from some Zanclea-like form \\bich has become 

 degenerate through its sessile habits. It can not swim, yet it has well-developed circular 

 muscles in the subumbrella and a distinct velum. 



Mnestra parasites Krohn. 



Mnf*i>, i /Hi'iifitef, KRIUIN, 1X53, Arclnv. Natures., Jalirg. 19, p. 178. CLAIS, 1875, Vi-rli.indl. /.mil. Buun. Gi-M-ll., \Vu-n. 

 Bd. 25, p. 9, taf. i. HAF.C'KEL, 1880, Syst. dor MrduM-n, p. 653. GUNTHKK, 1903, Mmhnl. Znol. Sta. Ni-a|vl, lid. id. 



p. 35, plates l, 3, 42 figs. 

 Mncstrii parasitica, FEWKES, 1884, American Naturalist, vol. iS, p. 197, figs. 4, 5. 



5' 



Fid. 50.- Mnestra parasites, from Florida, after Kc\\kt*s, in Aincr. Natu- 

 ralist, 1884. 



Fn.. 51. Mnestra parasites^ after Giinthrr, in Mitth. Zool. Sta. Nc.ip 

 Bell turned inside out, showing iiunit]i-|>.irt -, and cauti 

 exumbrella to be cup-shaped. Medusa hat. 3 \vcll-lc\r1f>pi-<l 

 tentacles. 



FIG. 52. Ctenaria ctenophora, after Hacckc], 1879. 



This minute, degenerate, highly variable medusa is parasitic or commensal upon the 

 mollusk Phvilit'hrjf. Its germ cells appear to migrate into the body of the PAy///rAo where 

 they develop. 



