SPIRORBIS. 385 
Agassiz' (1866) gave a good account with figures of the development of Spirorbis spirillum, 
and this agrees with the condition of the same form on our shores. The ova are deposited 
in the tube, the embryo having eyes, bristles and partially developed branchie before it 
leaves the egg. Its pelagic life is brief, and within twelve hours it settles on a suitable 
site and forms a minute calcareous tube. 
Claparéde® (1868) alludes to the reproduction of Spirorbis levis, De Quatrefages, in 
which he found ova in the first two segments of the abdomen. These ova made 
their way through the wide peduncle to the operculum, where they developed. The cavity 
of the peduncle is separated from that of the operculum by a membrane, which must be 
pierced by the ova or absorbed. The spermatozoa occur behind the third segment of the 
posterior region. 
Levinsen® (1883) enters nine species in his list of northern Polycheeta, and in addition to 
the nature of the tube, he uses the structure of the collar-bristles in separating them. 
De St. Joseph* (1894) describes the development of his Mera pusilla (Spirorbis pusil- 
loides, Bush), in which the ova occur in the two anterior segments of the abdomen, the suc- 
ceeding region having the sperms. Whilst the cavity of the peduncle is in communication 
with the ccelom, the developing ova in the operculum are separated by an oblique calcareous 
plate, which, however, may permit the passage of ova into the transparent operculum. The 
embryo has two eyes and a frontal palpocil, three segments and a rudimentary digestive 
canal containing the brownish-red yolk. S. pusillus is closely related to S. Pagenstechert, 
De Quatref. 
Miss Schively° states that Sprrorbis borealis has two breeding seasons, viz., from the 
middle of June to the middle of July, the other extends through the month of August. The 
egos escape through the operculum, which has a moveable translucent plate of lime. The 
reproductive glands occur on each side of the stomach. She appears to place ova and 
sperms in the same region. Miss Bush thinks she refers to Spirorbis Pagenstecheri, De 
Quatrefages, and further adds that this is probably the species studied by Fewkes® as Sp. 
borealis ; also, that the Sp. spirillum of Agassiz (1866) is S. borealis, Daudin=Sp. spirorbis, 
Linneus. She further notes that the embryos in Sp. validus and S. granulatus (non L.) in 
the operculum had well-developed bristles, and each was concealed by a white patch, which 
under pressure split into short rods, which dissolved in acid. 
An able and well-illustrated memoir on the genus Spirorbis and the species placed under 
it was published by MM. Caullery and Mesnil’ in 1897. They gave a brief historical account, 
the taxonomic characters of note, a description of the species, with a table for diagnosis, 
and lastly they considered the position of the Spirorbids in the Family Serpulide, their phylo- 
geny and distribution. They place less value on the form of the tube than on the structure 
of the animal, though in their synoptical table such forms the primary division, viz., tube 
1 «Ann. Lyceum Nat. Hist. N. York,’ vol. viii, p. 318, pt. vu, figs. 20—25. 
2 “Suppl. Annel. Neap.’ p. 159. 
> “Meddel. nat. Forh. Copenhagen,’ p. 205. 
4“ Annal. Sc. nat.,’ 7° sér., t. xvul, p. 352, pl. xin, fig. 391. 
» “Proc. Acad. Se. Philad.,” 1897, pp. 153—160, pls. i—un. 
6 On the larval form of S. borealis, ‘American Naturalist,’ xix, p. 247, pls. x1, xu. 
7 «Bull. Sc. France et Belgique, ser. iv, ix, p. 185, pls. vii—x. 
