TRACHYNEMA DIGIT ALE. 



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Trachynema digitale A. AGASS. 



Medusa digitalis FAB. Faun. Groenl. No. 361. 1780. 



Tunis (Circe') digitalis MORCH (non Forbes). Bcsk. af Gronl., p. 95. 1857. 



Eirene digitale ESCH. Syst. der Acal., p. 95. 1829. 



There is considerable doubt as to the specific difference of this spe- 

 cies of Trachynema from the English Circe of Forbes, and from the 

 Circe camtschatica of Brandt, the series of young observed at Nahant 

 being the only one which gives us any measure of the changes one 

 species undergoes during its growth. It is evident from the figure of 

 Forbes that the genital organs are but slightly developed ; in the north- 



rig. 82. 



western species the only specimens observed were all males, while the 

 only adults of this species obtained on our coast were females. This 

 question must be left undecided until we have a complete history of the 

 English species. 



The adult medusa (Fig. 81) is characterized by the thinness of the 

 bell, the great size of the gelatinous proboscis, which extends nearly to 



Fig. 81. Adult female Trachynema, seen in profile ; magnified. 



Fig. 82. Actinal view of the veil and circular tube of a very young Trachynema. c, c, c, c, 

 tentacles opposite the chymiferous tubes ; greatly magnified. 



Fig. 83. Profile view of a part of the circular tube to show the folds of the veil, e, one of the 

 pedunculated marginal capsules ; t, young tentacle ; v, folds of the veil ; somewhat more magnified 



than Fig. 82. 

 NO. II. 



