

1905.] Cephalodiscus (C. nigrescens) from Antarctic Ocean. 401 
being secreted in succession, serve to shorten the tube; the increase in the 
length of the tube is effected by additions of “test” to its free margin and 
over the whole surface of the colony. The tubes do not branch, and the 
length of the inhabited part of each is about 10 or 12 mm., and the width 
1-2 or 1°3 mm. 
The polypides are deeply pigmented and appear black to the naked eye. 
The pigmented cells are superficial, and are in reality brownish-yellow cells 
with one or two black spots of small size. The brownish-red patches which 
in C. dodecalophus are found around the oviducts, and the red curved line that 
passes across the buccal shield, are present also in the new species. 
The polypide is about three times as long as that of C. dodecalophus. The 
length of the body from the front of the buccal shield to the end of the 
visceral mass is 4°5 mm., whereas in C. dodecalophus the corresponding 
measurement is 1‘5 mm. The body is about 1 mm. wide, and fits fairly 
closely in the tube. 
Each polypide has from two to nine buds of various sizes attached by longer 
or shorter stalks to the extremity of its stolon. The stolon is short and stout, 
and in most of the polypides is directed parallel to the long axis of the body, 
and away from the plumes. 
There are 14 plumes in most of the individuals, but the number varies 
from 12 to 16. The axes of the plumes are broad and massive and of a black 
colour, and they do not terminate in the nearly spherical swellings that are 
found in the Challenger species C. dodecalophus. The pinnules are 
numerous and closely set, and they are not black, although microscopic 
examination shows that some of the pigmented cells are present on them. 
The stomach is not dilated and globular as it is in (C. dodecalophus ; it 
possesses a pointed czecum which passes up between the pharynx and the 
intestine and terminates between the gonads. The gonads consist either 
of two ovaries, of two testes or of an ovary and a testis. The three kinds of 
individuals are not distinguishable by any external features, and are not. 
restricted in their distribution; the same branch of the colony may have 
male, female, and hermaphrodite individuals, and no distinction can be drawn 
as regards sex between the individuals found in the basal, middle and more 
terminal portions of the same branch. 
The ccelom is divided, as in C. dodecalophus, into a pair of large abdominal 
cavities, a pair of collar cavities opening by collar pores close to the gill slits, 
and an unpaired cavity in the buccal shield opening by a pair of “ proboscis 
pores ” almost immediately above the stalk of the shield. 
This new species of Cephalodiscus is clearly marked off from C. dodecalophus 
by the massiveness of the colony, the blackness and the large size of the 
VOL. LXX¥VI.—B. 2: 
