24 W. G. RIDEWOOD. 
” 
a “lip” to the margin of each tube—and as apical growth continues and they 
themselves come to occupy positions successively more remote from the apex, they 
make their tubes longer and longer by additions to the margin, and they fill in the 
spaces between the tubes with softer common test, so that the part of the branch in 
which they occur becomes thicker and thicker. Since, apparently, this makes the 
tubes uncomfortably long, a shortening of them is effected by the successive 
formation of concave septa at the basal ends at such a rate as to leave the inhabited 
part of each tube about 8 or 12 mm. in length.* 
Polypides. 
The polypides are deeply pigmented and show conspicuously through the test. 
Most of them are in a state of contraction, and their plumed ends are situated 
about 5 mm. from the openings of the tubes in which they dwell; a few, however, 
are moderately expanded, and the plumes of these project slightly beyond the 
openings of the tubes. Not more than one fully-grown polypide is found in each 
tube, but from two to nine buds of various sizes are connected by their stalks with 
the end of the stolon of the individual to which the tube may be said to belong. 
The buds are usually crowded at that extremity of the polypide which is farthest 
from the opening of the tube. Lying freely in the tube in the vicinity of the 
buds an ovum sometimes occurs, rarely two or three; the ovum is oval and 
yellowish-white, and measures ‘5 by °6 mm. or ‘6 by ‘7 mm. The ova are seen 
in figs. 3 and 4 as,small whitish oval patches. 
The polypide is about three times as long as that of Cephalodiscus dode- 
calophus. 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, the interior of which is not more than 1°2 or 1°3 mm. across. 
When removed from its tube, a polypide and its buds present the appearance 
shown in fig. 7, plate 8. The buds are contracted and have their stalks twisted about 
one another in a manner which is obviously unnatural and is doubtless caused by 
the irritation set up by the fluid in which they were killed. With a little care the 
stalks of the buds of the formalin-preserved material can be unravelled (fig. 8) ; 
the material fixed in Perenyi’s fluid and that fixed in picric acid solution is, 
however, too brittle to allow of any disentangling of the stalks. 
* The above was written before the publication of Harmer’s report on the Pterobranchia of the ‘ Siboga’ 
Expedition, and it is interesting to note that in one of the new species described by him (C. levinseni) the 
polypides are similarly isolated, each tube of the tubarium being occupied by one polypide and its buds, and 
that the explanation of the growth of the colony which he puts forward (10, p. 11), includes as its essential 
feature the migration of the buds from the parental tubes, their crawling over the surface of the colony, and 
their subsequently establishing themselves in a suitable situation upon the surface, where they secrete tubes of 
their own. (Later note, dated Sept. 15, 1906:—The manuscript of the descriptions of C. nigrescens and C. 
hodgsont (pp. 20-62 of this Report) was completed in August 1905; the first nineteen pages of the Report were 
written in the summer of 1906). 
