AGLAOPHENIA CONSTEICTA. 47 



Aghophenia bispinosa is a beautiful species, and is surpassed in size by 

 very few hydroids. The proximal part of the stem is composed of a 

 congeries of tubes (PI. XXVII.), which at rather regular intervals become 

 curiously contorted into knot-like projections, and which, at the extreme 

 proximal end, become separated from one another, and here form a large 

 entangled mass of hydrorhizal filaments. Knot-like projections of quite a 

 similar kind occur in the European Aghophenia myriophglla. Towards its 

 distal extremity the stem loses its polysiphonic or fascicled condition and 

 becomes monosiphonic. In the specimens examined the pinnse were borne 

 along somewhat less than the distal half of the stem. 



The hydro thecae are remarkable for the long, strong tooth which 

 projects from the front of the margin ; but a still more remarkable 

 character is found in the presence of a second mesial nematophore 

 situated on the internode, just behind the normal one and unconnected 

 with the hydrotheca. (PI. XXVIII.) 



The corbulce (Fig. 3) are very beautiful. They closely resemble those of 

 A. distans, present the same elements in their formation, and, like these, 

 afford a most instructive illustration of the essential morphology of the 

 organ. The peduncle which connects them with the common stem, and 

 which consists of the proximal portion of the pinna, which, in its ter- 

 minal portion, becomes transformed into the corbula, is vinusually long 

 (Fig. 4), and consists of five scarcely altered internodes with their hy- 

 drothecas; an additional mesial nematophore, however, is developed near 

 the proximal end of each of these internodes. 



Aglaophenia constricta. 



PI. XXIX. Figs. 1-4. 



Trophosomc. — Stem attaining a height of about eight inches, thick, 

 fiiscicled, springing from an entangled mass of wiry filaments, and send- 

 ing off numerous, irregularly disposed, simple branches, which carry 

 alternately disposed pinnte, three pinnte springing from every internode. 

 Hydrothecas with the distal half expanded and separated from the proxi- 

 mal part by a deep constriction ; margin with four broad teeth. Supra- 

 calycine nematophores slightly overtopping the margin of the hydro- 

 theca ; mesial nematophore nearly equalling in length the height of 

 the hydrotheca, to which it is alinost entirely adnate ; cauline nema- 



