62 W. G. RIDEWOOD. 
the posterior lobe grows backward and downward; it is thinner than the anterior 
part of the shield, and maintains this relation throughout life. 
By the time the shield is so far differentiated as to possess a stalk or pedicle 
attached to the middle of its dorsal surface, the “body” or metasome is_pear- 
shaped, and a second pair (fig. 56), and third, and fourth (fig. 57) pairs of plume-axes 
make their appearance. The bud is at this time capable of remarkable change of 
form, and an eight-plume bud may show a long “body” and stalk, and a cupped 
shield with an obvious pedicle (fig. 58), or, more usually, a flattened shield, 
attached at its middle, but with no clear pedicle, and a short and wrinkled “ body” 
and stalk (fig. 57). As a rule, buds that have reached the same stage of 
development, so far as can be judged by the number of plumes present, are of 
approximately the same size, but it is to be noted that the eight-plume bud shown 
in fig. 58 is exceptionally large. 
The red line of the buccal shield begins to appear at about the stage when 
the fourth pair of plume-axes are hemispherical knobs only, or are losing their 
hemispherical shape and are becoming elongated (text-fig. 17, B, p. 54). 
SUMMARY OF RESULTS. 
1. A new species of Cephalodiscus (C. hodgsoni) is placed on record (p. 3), 
and descriptions are given of the two species obtained by the ‘ Discovery,’ namely, 
C. nigrescens and C. hodgsoni (pp. 20-49 and pp. 49-62). 
2. A new sub-generic name /dicthecia is given for the inclusion of those species 
of Cephalodiscus (eg. C. nigrescens and C. levinseni) in which the polypides reside 
in separate tubular cavities in the tubarium (p. 7), and the sub-generic name 
Demothecia for those species in which the polypides live together in the same cavity. 
3. A review is given of the six recorded species of Cephalodiscus, namely, 
dodecalophus, hodgsont, gracilis, sibogae, nigrescens and levinseni (pp. 7-11), also a key 
to the identification of these (pp. 11-12). 
4, Since the tubes of the tubarium of C. nigrescens are entirely separated and 
show no signs of having been continuous at an earlier stage of development, a 
suggestion is offered as to the behaviour of the polypides in the building up of the 
tubarium (p. 23). 
5. Descriptions and semi-diagrammatic figures are given of sections of the 
polypides of C. nigrescens taken through structures of particular interest (pp. 34-41). 
6. The “ problematical body” of Harmer, supposed by that author to consist 
of lamellae, probably of a muscular nature, is shown in the case of C. nigrescens 
to be formed, not of lamellae, but of obliquely interlacing cross-striped muscle 
fibres (pp. 41-48). 
7. In both of the new species obtained by the ‘ Discovery’ there are 
hermaphrodite individuals, with one ovary and one testis, as well as males and 
