TUNICATES AND ASCIDIANS 477 
ored, but otherwise it is repulsive in aspect. The apertures are 
wide apart; one orifice is eight-lobed, the other six-lobed. 
A. amphora. Form usually globular, but more or less irregular ; sub- 
stance something like rubber. Found of all sizes adhering in clusters to 
stones, shells, and piles, and usually covered with marine growths. The 
color is grayish-brown. 
A. callosa. Body depressed, usually oval, but varying in shape; 
thick, fleshy, translucent; surface uneven; apertures dark purple and 
XEN) Found at low tide adhering to stones and shells. (Plate 
COMPOUND ASCIDIANS 
Ascidians of this group form fixed colonies, and are embedded 
in gelatinous material, the animals having a common test, but not 
being united by any internal union. The colonies thus formed 
are flat and incrusting, or are branched and lobed, or sometimes 
elevated on stalks. The zodids are in some cases dotted irregu- 
larly over the entire surface, in others are in rows, or again are 
in groups. They have various colors—purple, yellow, blue, gray, 
and green. They are common on eel-grass, the piles of wharves, 
the bottoms of boats, and so on. 
Genus Botryllus 
B. gouldii. This species forms thick, fleshy, translucent incrustations, 
often several inches in length and a quarter of an inch wide, over eel- 
grass, the piles of wharves, and other objects. Sometimes, at the end of 
summer, small objects are completely covered with the luxuriant growth 
of this compound ascidian. The zodids form circular or elliptical 
groups, often as many as fifteen surrounding each orifice, looking like 
minute stars. The colonies vary in color. Often on the same stem of 
eel-grass will be found separate colonies varying in this respect. In 
some the ground-color will be olive-green specked with white, while the 
zodids are purple, marked with other colors ; again the arrangement is 
quite different. 
Genus Amarecium 
A, pellucidum. A massive compound ascidian, smooth, translucent, 
and gelatinous, which forms large, hemispherical, complex, irregular 
masses six inches or moreindiameter. Itis usually covered by adhering 
sand. The mass consists of club-shaped lobes, which rise from a common 
base. Each lobe contains a central orifice around which long, slender 
zoids, sometimes an inch long, are grouped. These masses are so abun- 
dant in some places that they cover the bottom for considerable spaces. 
They are found in deep water from Cape Cod to North Carolina. 
