20 SABELLARtA SPINULOSA. 



aperture is richly ciliated, and Mr. Watson found that when severed from the body the 

 anal aperture contracted at regular intervals of four or five seconds. 



Habits. — This is one of the forms which aids in counteracting the effects of the borings 

 of Pholas and other forms, and in resisting the erosion of the sea in every climate. It is 

 agile in movement in its tube, to which it clings with great pertinacity, but is somewhat 

 sluggish when removed, lying in the vessel with the tentacles ventral, and the branchiae 

 generally though not always dorsal. 



Arnold Watson observed in a living example that the tail at times assumed a 

 moniliform outline, and that the bristles posteriorly were in constant motion, apparently 

 assisting in the circulation of the water and the expulsion of waste matter. The long 

 liook-lamellas were always in contact with the lining of the tube as the body moved 

 forward or backward. The same observer (in MS.) considers that this species is that 

 best fitted for study from its hardihood, living always under water, whereas S. alveolata 

 prefers alternations of air and water. In Scotland, however, S. spinulosa covers 

 considerable areas between tide-marks, so that it follows similar habits to S. 

 alveolata. 



Mr. Watson considers that rotation of the body on the long axis of the annelid is 

 produced by the bristles on the third, fourth and fifth feet, which are so arranged that a 

 cross-thrust can be obtained, the small ventral fascicles being directed forward at a right 

 angle to the body, whilst the broad lateral fascicles of short bristles are directed backward 

 as if to thrust the body out of the tube. 



Reproduction, — Breeds in May at Plymouth (W. Garstang) ; September (Allen) 

 mature specimens in September in Ireland (Southern). Arnold Watson found the ova 

 collected in Wales in June of a deep pink hue, and a specimen only a quarter of an inch 

 long discharged about sixty. They are larger than the ova of S. alveolata. Dehorne 1 

 observed that the number of the chromosomes in the spermatogenesis of this species was 

 eight, so that it agrees generally with what Schriener found in Toinopteris and Ophryo- 

 trocha, The larvae are abundant in the tow-nets during the summer months off the east 

 coast of Scotland. 



Fauvel' 2 notices that the larvae occurred at St. Vaast-la-Hougue in July. 



The tubes are composed of coarse shell-gravel, or sand-particles more or less neatly 

 cemented together, and forming as a rule at the Bast Rocks, St. Andrews, large masses, 

 apparently having no very definite arrangement, though fracture reveals many tubes 

 running in the same direction, yet they are often sinuous. Apparently each tube is closed 

 posteriorly. Single tubes occur on shells and stones. The materials of which the tubes 

 are composed show endless variety ; fine sand-grains may form one part of the tube, 

 coarse shell-gravel another, and larger fragments of shells, or Balani, may be on a third 

 region. Internally the tube is lined by the secretion, and a fold of this sometimes 

 occurs at the aperture, which is slightly dilated, the margin being inclined outward so as 

 to make a firm hold for the paleae. At Lochmaddy, North Uist, the tubes, composed of 

 sand-particles, are met with singly as long, wavy diminishing tunnels, the posterior end 

 being pointed. This locality was in strong contrast, for instance, with St. Andrews, 



1 'Assoc. Franeaise ravancem. sc. Lille/ 1909, p. 124. 



2 'Ann. Sc, nat. Zoo!./ 9 e ser. ; t. x, p. 208. 



