REPORT ON THE TUNICATA. 
319 
The Mantle is fairly strong. The muscle bands are delicate but regular. 
The Branchial Sac is large and well developed. The stigmata are very long and 
narrow. The transverse vessels are comparatively slight. 
The Dorsal Lamina is represented by a series of long triangular languets. 
The Tentacles are long and thin. They are numerous and of two sizes, but are not 
regularly arranged. 
The Dorsal Tubercle has rather a large aperture. 
The Alimentary Canal is fairly large, but it does not extend, far behind the branchial 
sac. The stomach is small and smooth -walled. 
The Reproductive Organs are not conspicuous. The testis is composed, of a number 
of pyriform vesicles which join a spirally coiled vas deferens. The tailed larvae are 
very large. 
Locality. — Station 320, February 14, 1876; lat. 37° 17' S., long. 53° 52' W.; 
depth, 600 fathoms; bottom temperature, 37°’2 F.; bottom, green sand. 
One specimen of this interesting form was obtained from the considerable depth of 
600 fathoms, off the east coast of South America. Seen from the side, the colony is 
distinctly reniform (PI. XXXVII. fig. 1), having a convex upper and a concave lower 
surface and two rounded ends. An end view, however (PI. XXXVII. fig. 2), shows that 
the mass is really hollow, being traversed throughout the greater part of its length 
by a large axial cavity which opens to the exterior by a terminal circular orifice about 
7 mm. in diameter (PI. XXXVII. fig. 2, and PI. XXXVIII. fig. 1). Apparently the 
colony was not attached, but as there is a Polyzoon adhering to its outer surface, 
it was probably not free-swimming but lay on the sea-floor. 
The extraordinary shape of the colony recalls the arrangement seen in Pyrosoma, 
where the Ascidiozooids and their investing mass form the walls of a hollow cylinder 
closed at one end. In Pyrosoma, however, while the branchial apertures of the 
Ascidiozooids open on the outer surface of the colony, the atrial apertures open on 
the inner surface into the axial cavity of the colony (see fig. 10, C), which is thus 
converted virtually into a common cloacal cavity, and the terminal aperture into the 
sole excretory orifice for the whole colony. In the present species this is not the case. 
The whole surface, both the outside of the specimen and also the lining of the axial 
cavity, is morphologically the outer surface of the colon}?", and the branchial apertures of 
the Ascidiozooids are found distributed all over it (see fig. 10, B). In this respect, 
therefore, Ccelocormus huxleyi presents an arrangement intermediate between that found 
in the typical Compound Ascidian (see fig. 10, A), where the colony is attached and 
more or less rounded, and the apertures of the Ascidiozooids open upon a flat or convex 
upper surface, and that peculiar to Pyrosoma (see fig. 10, C), where the colony is free- 
swimming, cylindrical, and has an axial cavity into which the atrial apertures of the 
