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. cattosa. Body depressed, usually oval, but varying in shape ; 

 thick, fleshy, translucent ; surface uneven ; apertures dark purple and 

 prominent. Found at low tide adhering to stones and shells. (Plate 

 LXXXV.) 



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 iiicrusting, or are branched and lobed, or sometimes 

 elevated on stalks. The zooids 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 zooids 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 

 zooids are purple, marked with other colors ; again the arrangement is 

 quite different. 



GENUS Amarcecium 



A. pelluddutn. A massive compound ascidian, smooth, translucent, 

 and gelatinous, which forms large, hemispherical, complex, irregular 

 masses six inches or more in diameter. It is 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 

 zooids, 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. 



