SPIRORBIS BOREALIS. ALS 
this form inside the operculum, but he found it different. The same form was noticed by 
Leschke! at Kiel. 
At St. Andrews the ova are small at the beginning of March and are situated toward 
the termination of the stomach, some being in front and some behind the organ. The sperm- 
cells (for they are undeveloped) fill the body-cavity in the same region as well as extend to 
the tip of the tail. These cells are ovoid or elliptical, with a central streak. The enormous 
masses of the male elements are in contrast with the comparatively limited number of ova. 
In Lister’s ‘Historize Conchiliarum’ (1685) there is in the Index, after Dentaliwm, on 
Plate 547, fig. 4, Serpula decussata, and in Plate 548, fig. 1, Serpula lwmbricalis and S. 
anguina. The relationship of these to known forms could not be determined. 
Montagu (1803) noticed a variety of the tube with the mouth erect, and sometimes 
with one or two volutions projecting spirally upward. He termed the operculum the 
proboscis. Cosmovici (1880) observed that Spirorbis communis is hermaphrodite, as in 
the species described by Pagenstecher, the ovaries occurring in the middle of the body 
and the spermaries in the posterior region. 
Spirorbis affinis, Levinsen,? looks not unlike S. borealis. He does not give a figure 
of the bristles, or furnish accurate data for identification. 
In American literature Spirorbis borealis and Sp. spirillum appear to be often confused. 
Thus Miss Schively describes the eggs of Sp. borealis as passing through the operculum, 
which has a moveable plate of tissue, whilst Sp. spzrillwm has an opercular brood-pouch. 
As Miss Bush observes, she probably in the latter instances refers to Sp. pagenstecherr, yet 
the synonymy of the American Serpulids and Sabellids is puzzling, and some of the new 
species may yet be linked on to the old. 
Caullery and Mesnil (1897) consider that the Circeis armoricana of De St. Joseph is only 
a variety of this species, somewhat larger, with more abdominal segments, and a smaller 
talon under the operculum, and that they had observed intermediate links between the 
two. Miss Pixell seems to have the same opinion. The S. malardi, Caullery and Mesnil, 
is a Closely allied form—except for the spire (Paralwospira) and the presence of four setigerous 
segments. They observe that a certain amount of polymorphism characterises both tube 
and operculum; those examples which are fixed to stones have generally a smaller umbilicus 
and are less regularly spiral than those on algze. The operculum on those attached to stones 
has the talon (basal division) separated by a constriction and often bifid. They found nine 
branchize in the young, ten in the old. Their figures of the collar and the sickle-shaped 
bristles are good. 
Wollebek’s figure (6) shows a smooth terminal blade, and the absence of minute details 
indicates that the kind of plate in the memoir is perhaps not well adapted for such 
illustrations. 
Loye® (1908) found Diatoms and other alge and débris imbedded in the calcareous matter 
of the tube. He gives an account of the general anatomy of this species, with the physiology 
of the parts, in the several regions, viz., the cephalic, the thoracic, the next without bristles, 
and, lastly, the abdominal region. He found definite transverse muscles only in the thoracic 
1 “Wiss. Meeresuntersuch.,’ Bd. v, p. 128, 1902. 
* ‘Greenland,’ pp. 200 and 207, Tab. iii, fig. 7. 
§ “Die Anat. von S. borealis,” Spengel’s ‘ Zool. Jahrb.,’ Bd. xxvi, pp. 305—354, Tat. xvi—xvii. 
