HYDROIDS OF THE WOODS HOLE REGION. 
335 
Hydractinia polyclina Ag. Fig. 12. 
(Cont. Nat. Hist. U. S., IV, p. 227.) 
Trophosome . — Colony composed of thickly crowded persons arising from an incrusting plate beset 
with jagged spines and overlaid with coenosarc. Hydranths slender, gradually increasing in size 
from proximal to distal end, tentacles 
numerous, filiform, arranged in sev- 
eral closely approximated whorls, 
which are so closely set as to appear as 
one whorl at the base of the rather low 
conical proboscis. Spiral zooids gen- 
erally situated on the borders of the 
colony and with a number of nema- 
tocyst batteries around the distal end. 
Gonosome . — Gonophores borne 
on sexual persons which are much 
stouter and shorter than the hy- 
dranths, and have numerous batteries 
of nematocysts around the conical 
proboscis, but no tentacles. No free 
medusse. 
Color . — Hydranths white, tinged 
with red. Gonophores, which give 
the characteristic color to the colony, 
bright red. 
Distribution . — Found growing on 
gasteropod shells inhabited by hermit 
crabs, on the bare rock, or on the piles 
of wharves. The writer has found them among the colonies of Tubular m erocea on the U. S. Fish Com- 
mission wharf at Woods Hole. 
I have carefully compared this species with II. echinata from England, and found that the two 
are quite distinct, as claimed by Agassiz. Aside from the characters as given by him, I find that the 
European form has very much larger hydranths than the American and much less numerous tentacles. 
PODOCORYNIDA5 (modified). 
Trophosome . — Hydranths with a single whorl of filiform tentacles around the base of a conical 
proboscis. Hydrorhiza a reticulate network of stolons invested with perisare and usually beset with 
jagged spines. 
Gonosome . — Gonophores growing in a circlet around the basal part of the hydrantli body, and 
producing fixed sporosacs or free medusse with 4 radiating canals and 4 or 8 marginal tentacles with 
eye-spots at their bases. 
STYLACTIS. 
Trophosome. —Hydranths sessile, without evident perisare, slender, growing from a hydrorhiza 
composed of a network of anastomosing tubes which are not covered with naked coenosarc and which 
usually bear chitinous spines. 
Gonosome . — Sporosacs borne on the hydranth body just below the tentacles and producing 
medusse with 8 rudimentary tentacles and no mouth. 
Stylactis hooperi Sigerfoos. Figs. 13 and 85. 
(American Naturalist, xxxm, No. 394.) 
Trophosome . — Hydranths exceedingly slender and attaining a height when alive of about three- 
fourths inch. Tentacles in a single whorl, very variable in number, the average, according to Sigerfoos, 
being 18 to 25. Hydrorhiza covered with a felting of diatoms, etc., but with no covering of naked 
ductive persons. C. Spiral zooids or fighting persons. 
coenosarc. 
