{375] INVERTEBRATE ANIMALS OF VINEYARD SOUND, ETC. 81 
The Ascidians are generally uncommon on muddy shores, but wherever 
the eel-grass flourishes, and especially in sheltered situations, the Molgula 
Manhattensis (p. 311, Plate XX XIII, fig. 250) is usually to be found ad- 
hering to it. The Botryllus Gauldii (Plate XX XITI, figs, 252, 253) is also 
frequently found growing upon the eel-grass in such situations, as well 
as upon the piles of wharves, bottoms of boats, &c. This species was 
found in great profusion upon the eel-grass in Little Harbor, at Wood's 
Hole, and in Waquoit Pond. In both these localities the water is nearly 
pure and but slightly, if at all, brackish. Butit has also been found by 
Professor D. C. Eaton on the piles at Brooklyn, New York, where the 
water is more brackish. This species when young forms thin, soft, circu- 
lar or oval incrustations covered with stellate clusters of the minute ani- 
mals, (fig. 253,) which are imbedded in it; each of these has a small 
circular orifice toward the outer end, opening into the gill cavity, and 
another orifice opening into a larger cavity in the center of the cluster, 
which is common to all those in the cluster; and it has a central exter- 
nal orifice, through which the waste water from the gills, the fieces, 
and the eggs are discharged. These young colonies begin to appear in 
June and grow very rapidly, new individuals being formed by buds that 
originate from the first ones in rapid succession, so that in two or three 
weeks the small colonies will increase from a quarter of an inch in 
breadth up to three or four inches, if they be situated on a flat sur- 
face and have room to spread. If upon the stem or leaf of the eel- 
grass they will extend entirely around it, and perhaps several inches 
along its length, if not opposed by other colonies. At the same time the 
crusts increase very much in thickness. Thus by the end of the summer, 
the eel-grass, algve, stems of hydroids, &c., often become completely 
covered up by the luxuriant growth of this curious compound animal. 
The colors of this speeies are extremely variable and often very elegant, 
and it is seldom that two colonies can be found with precisely the same 
pattern of color. Growing upon the same leaf of eel-grass, many dif- 
ferent colonies may often be found, each showing a different arrange- 
ment of the colors. 
In one of the most common varieties the general color of the common 
tissue between the stellate clusters is dull olive-green, thickly specked 
with small flake-white spots, which are formed by the enlarged terminal 
portion of stolon-like processes, which bud out from the perfect individu- 
als composing the clusters, and are arranged somewhat in circles around 
the clusters; the lower portion of these stolons is usually yellow or 
orange, and the outer part deep purple, tipped with flake-white. The 
individual animals, or zodids, composing the stellate clusters, are deep 
purple, with the branchial orifice yellowish white, surrounded by a circle 
of orange; a short flake-white longitudinal line runs along the middle of 
the upper side, interrupted by the branchial opening, but this line is 
often represented only by two white spots; other flake-white spots are 
usually irregularly scattered over the outer end. 
