310 THE AMERICAN NATURALIST. [VOL. XXXV. 
Etudendrium capillare Alder. 
Of the distinctness of this species and £. a/bum, listed by Professor 
Nutting, I have grave doubts. It seems to me that Alder’s diagnosis of 
capillare coincides so closely with that of /. ¢ezwe as to render their identity 
highly probable. So also of &. album. Specimens taken at Woods Holl 
seem almost certainly identical with £. ¢ewwe, and therefore both should 
probably be merged under £. capzl/are, whatever slight differences there 
are being hardly greater than varied environment would easily explain. 
5. HyYDRACTINIDA. 
The Hydractinidz are so closely allied to the following family that it 
seems unfortunate that they were not originally merged ; the only easily 
distinguishable difference being in the free medusz of the latter in contrast 
with the fixed sporosacs of the former. In size, general habit, and mor- 
phology they are so closely identical that but for the gonosomes no differ- 
ence would be recognizable, though in Podocoryne the hydrorhiza seems less 
definitely covered with naked ccenosarc, — but even this differs greatly in 
specimens from different localities. 
In both polymorphism is a marked feature, at least three types of polyps 
being distinguishable : 
1. Feeding hydranths (trophopolyps), whitish in color and with numer- 
ous filiform tentacles, frequently appearing in alternately elevated and 
depressed order. 
2. Reproductive individuals (gonopolyps), more slender-bearing gono- 
phores in clusters below the tentacles, which are fewer in number than in 
the first and imperfectly developed. 
3. Spiral polyps, elongated individuals, 
wholly devoid of tentacles and with apex 
of body thickly beset with nematocysts. 
The entire colony arises from an in- 
crusting base which is thickly beset with 
jagged spines, the latter sometimes con- 
sidered a fourth type of individual. 
fydractinia echinata Fleming. 
(Hydractinia polyclina Ag., Cont. Wat. 
LLISE. 8 Sy) 
Trophosome: Colony composed of 
Fic. 7.— Aydractinia echinata. numerous polyps, as given above. 
Cees SS 2) Gonosome: Gonads as sessile sporo- 
sacs borne on distinct hydranths, gonopolyps, having but few tentacles. 
Medusoids never free. 
