388 THE AMERICAN NATURALIST. [Vor. XXXV. 
subsequent secretions as the hydranth grows, leaving the old hydrophore. In 
many cases the everted rim has on its inner margin a circle of small bright 
dots which are rather characteristic of the genus. Hydranths imperfectly 
retractile, elongate, and with conical hypostome. 
Gonosome : Gonangia of varying aspects, showing distinctive differences 
between male and female and affording easy means of distinguishing the 
sexes. Medusoids imperfectly developed, never free. 
1, H. halecinum Linn. (FIG. 25). 
Trophosome: Colony erect, rather rigid, subflabellate in form. Hydro- 
thecz alternate, somewhat tubular in form, and with everted rims. 
Gonosome : Gonangia borne in a series on the upper side of the branches ; 
those of the male elongate, slender, somewhat spindle-shaped, tapering below 
e b 
Fic. 25. — Halecium halecinum Linn. a, male; 4, female gonangia of same 
(enlarged). (After Hincks.) 
to their attachment by very short, slightly ringed pedicels. Female gonan- 
gia somewhat oblong, broader toward the distal end, and with tubular 
aperture nearer one margin. 
2, H. beanii Johnston. 
Trophosome : Colony of delicate, graceful form, somewhat dendritic, 
attaining a height of about two inches. Hydrothece with everted 
rims. 
Gonosome : Gonangia arising from near the base of hydrothece ; male, 
elongate oval; female, somewhat curved, with the aperture situated near 
the middle of the upper side. 
