376 W. G. Van Name — Bermuda Ascidians. 



cover the anterior end of the zooids about the branchial orifice 

 (often obscuring the ground color) or form a ring about it, or in 

 other cases a star-shaped area with about eight rays. Frequently 

 they are scattered over the mantle in small groups, on the bulbs of 

 the test-vessels, and often elsewhere. The white may be replaced 

 by pale greenish, light yellow or (in one specimen) even bright 

 orange. This light colored pigment disappears completely when the 

 animal dies, and the zooids become some shade of purple, purple-red, 

 or blackish, and the test loses most of the color it possessed during 

 life (even where it was quite dark colored) and becomes much more 

 transparent. 



Space will not permit of more particular description of the various 

 colors assumed by different specimens, all of which I consider no 

 more than individual variations of one and the same species. It is, 

 in many of its forms, among the most beautiful and brilliantly col- 

 ored of compound ascidians, and the name nigrum is by no means 

 appropriate, though black colonies do occasionally occur. Herdman 

 wrote his description from alcoholic specimens, which are often black 

 or nearly so. 



There are neai'ly always small groups of very large round cells 

 with purple or purplish red pigment on the mantle along each side 

 of the endostyle. What their nature or function is I am unable to 

 say. Such cells occur also in the varieties concolor and planum, 

 described below. 



The zooids in this species are rather small. In the contracted 

 state in which they occur in preserved specimens they do not average 

 over 1.5 mm in length. 



The mantle is (for this genus) fairly muscular and the zooids in 

 the contracted state are apt to assume the curved cylindrical form 

 which is well shown in fig. 54 and is rather characteristic of the 

 species. The mantle muscles consist of delicate fibers and are chiefly 

 developed in the dorsal region. The transverse vessels of the 

 branchial sac also have muscle fibers. 



There are about thirteen rows of stigmata and three internal lon- 

 gitudinal bars on each side. Between each of these there are about 

 three stigmata, but on each side of the dorsal lamina and endostyle 

 there are four or five. The tentacles are eight in number, larger 

 and smaller alternating. The atrial siphon is very large and forms 

 a capacious chamber with a large funnel-shaped opening, the anterior 

 lip of which is prolonged into a languet. The position, form and 

 length of the siphon varies according to the relation of the zooid to 



