[327] INVERTEBRATE ANIMALS OF VINEYARD SOUND, ETC. 38 
and thrown overboard, as is sometimes done, each ray has the power of 
reproducing all the lost parts, so that each fragment may, after a time, 
become a perfect star-fish. 
The color of this species is generally dark green or brownish green, 
with the madreporic plate bright orange; the males are more inclined 
to brown, and sometimes have a reddish tint. It is found all along the 
coast from Massachusetts Bay to Florida. 
The eggs of this species, like those of most other star-fishes, produce 
peculiar larve, entirely unlike the parents, and provided with vibrating 
cilia by means of which they swim about in the water, or at the surface, 
for a considerable time. The young star-fish develops within the larva 
and gradually absorbs the substance of the larva into its own organi- 
zation. 
The development of this and our other common species has been very 
fully described and illustrated by Mr. A. Agassiz. 
Of the Hydroids many species occur in the pools, or attached to the 
lower sides of overhanging rocks, or of stones that have an open space 
beneath them, or growing upon the Fucus and other sea-weeds at low- 
water mark. The most abundant of all is the Sertularia pumila, (Plate 
XXXVI, fig. 279,) which grows in small tufts of delicate branches on 
the stems and fronds of all the larger sea-weeds, and on the sides and 
lower surfaces of stones. Another beautiful species, the Obelia commis- 
suralis, (Plate XX XVII, fig. 281,) occurs at low-water mark and in tide- 
pools, attached to stones and sea-weeds. It is very delicate and much 
branched, and sometimes grows five or six inches high, though usually 
smaller. Atcertain times it produces small meduse in its urn-shaped 
reproductive capsules; these are discharged and swim free for sometime, 
haying sixteen tentacles when they become free. Several other spe- 
cies of this genus also occur attached to the sea-weeds at low-water. 
The most common of these is O. diaphana, which grows about an inch high, 
attached to the stems of Fucus. The Campanularia flecuosa is another 
similar hydroid, remarkable for its large reproductive capsules, in which 
meduse are developed that never become free. This species occurs 
in the pools at low-water, on weeds and stones, and also on the lower 
sides of overhanging rocks or the timbers of wharves. It is much 
more abundant farther north, as at Eastport, Maine, where it grows in 
profusion on the timbers of the wharves, hanging down from their 
lower sides, collapsed and dripping, while the tide islow. The Pennaria 
tiarella (Plate XX XVII, figs. 277, 278) is a very conspicuous and bean- 
tiful species on account of its much-divided black branches and numer- 
ous bright red flower-like hydroids. It occurs occasionally in the pools, 
and just below low-water mark, attached to stones, corallines, &c., but is 
more common in somewhat deeper water on rocky and shelly bottoms. 
The “file-fish” feeds on this species, and probably on other allied 
hydroids, for its stomach was found full of the stems and branches, 
cut up in fine pieces. Its broad, sharp-edged jaws are admirably 
