[389] INVERTEBRATE ANIMALS OF VINEYARD SOUND, ETC. 95 
tirely imbedded in the gelatinous mass that unites them together. They 
are arranged in circular, oval, or stellate groups, with a common cloacal 
orifice in the center of each cluster. The masses are usually pale orange- 
red, varying to yellowish and pale flesh-color. The stomach of each in- 
dividual is bright orange-red; the branchial sac is flesh-color, pale yel- 
low, or orange; the tubes and upper part of the mantle bright orange or 
lemon-yellow. 
The Botryllus Gouldii (p. 375, Plate XX XIII, figs. 252, 253) also fre- 
quently occurs on the piles of the wharves, creeping over the stems of 
Tubularians, the surfaces of other ascidians, fronds of alge, or on the 
surface of the wood itself. It also frequently forms broad, soft incrusta- 
tions on the bottoms of boats, floating timber, &ec. 
The Bryozoa are also usually quite abundant on the piles and timbers 
of wharves, &e. 
The Bugula turrita (p. 311, Plate XXXIV, figs. 258, 259) is one of the 
most common as well as one of the most elegant of these. It occurs at- 
tached to the adhering sea-weeds, &c., forming delicate white plumes. 
The Escharella variabilis (p. 311, Plate XX XIII, fig. 256) usually forms 
firm, coral-like incrustations, but when attached to hydroids and sea- 
weeds it spreads out into foliaceous or lichen-like, rigid, calcareous 
fronds, which are dull red while living. 
On the piles at Wood’s Hole the Bugula flabellata was also very abun- 
dant. This forms elegant circular or fan-shaped fronds, consisting of 
numerous repeatedly forked, flat, and rather narrow branches, on which 
the cells are arranged in about three longitudinal rows. This species, 
like others of the genus, bears very singular structures, known as avicu- 
laria, which, under the microscope, have the form and appearance of the 
stout, hooked beaks of certain birds, such as the hawk, owl, parrot, 
&c. These beaks are attached by flexible stems, and are provided in- 
ternally with powerful muscles by means of which they are constantly 
opened and closed, and can bite with considerable force. In this 
species these are attached to the sides of the cells, along the edges 
of the branches. Their office seems to be to defend the colony. against 
small parasites, and dirt of all kinds, which, unless thus removed, would 
soon cover up the cells and destroy the animals. In addition to these, 
various less conspicuous species often occur in abundance, especially 
Vesicularia gracilis ; V. dichotoma V.; and V. cuscuta. 
Of Radiata there are but few species in such localities, with the excep- 
tion of the Hydroids, which are usually very abundant. 
The green star-fish, Asterias arenicola, (p. 326, Plate XXXYV, fig. 269,) 
may occasionally occur adhering to the piles just below low-water mark, 
‘but it does not have this habit to such an extent as does the A. vulgaris, 
north of Cape Cod, for the latter is almost always to be seen in abun- 
dance on the piles of the wharves of the northern seaports, as at Port- 
land, Eastport, &c., and less abundantly at Boston. 
One of the most beautiful, as well as one of the most abundant, of 
