154 
THE VOYAGE OF H.M.S. CHALLENGEE. 
bands of considerable size. Weaker longifudinal muscles are also present. The 
branchial sphincter is strong. 
The Branchial Sac is long and rather narrow. It is very simple in its structure, 
consisting merely of transverse and longitudinal vessels intersecting at right angles, so 
as to form a large-meshed network. The meshes are a little longer vertically than 
transversely. The transverse and the longitudinal vessels are of the same size. They 
contain a few rather large muscle fibres. 
The Tentacles are large. There are at least twelve, and they are all of much the 
same size. 
The Dorsal Lamina is formed of a series of closely placed, irregularly triangular 
languets. 
The Alimentary Canal is large. 
The Reproductive Organs are large. They extend behind the intestine in the form 
of a long post-abdomen. Both ova and spermatic vesicles are present. 
Locality. — Station 147, December 30, 1873 ; lat. 46° 16' S., long. 48° 27' E.; depth, 
1600 fathoms ; bottom. Diatom ooze; bottom temperature, 34°‘2 F. 
This interesting form is one of the few deep-sea Compound Ascidians. It was 
trawled at Station 147, between the Cape of Good Hope and Kerguelen Island, from a 
depth of 1600 fathoms. 
In its fungLis-like form it resembles some of the species of Colella. The shape, how- 
ever, varies considerably in the six specimens. One of the colonies was considerably 
damaged ; a second is very small (PI. XXL fig. 3). The remaining four are of about the 
same size. In these the head is decidedly discoid in one specimen only (PI. XXI. fig. 2). 
In two others it is flattish above and conical below. In the other colony it is in an inter- 
mediate condition. The- three figures (PI. XXI. figs. 1, 2, 3) show the amount of 
diflference in the specimens. The upper surface of the head is irregular, being raised into 
slight elevations formed by the anterior ends of the Ascidiozooids. In some places the 
free edge of the disk is bent downwards so as to form a prominent ridge around 
the lower surface. The peduncle is thickest at the base of attachment, where it spreads 
out considerably. In one case this expanded base is over 13 mm. in diameter. Shells 
of Foraminifera and fragments of manganese are attached to and imbedded in the 
lower part of the peduncle. From the base the peduncle tapers upwards to its 
narrowest point just below the head, and then expands rapidly to pass into the 
under surface (see PI. XXL fig. 1). 
The Ascidiozooids are very large ; including the reproductive organs they measure in 
some cases as much as 13 mm. in antero-posterior extent (see PI. XXL figs. 4, 5). They 
are, however, rather narrow ; the widest point is in the abdomen where the stomach 
is placed. The Ascidiozooids are not arranged with any regularity. They seem, however. 
