362 OWENIA FUSIFORMIS. 



and the multitude of hooks for grasping the inner lining, and thus enabling the animal 

 to screw it upwards (Watson). The tube readily stretches in the living form, the grains 

 or fragments being sloped in extension and erected in contraction. Besides leaving the 

 sand and dragging the tube on the surface, it may be exposed by storms ; at any rate 

 large numbers are occasionally found in the stomachs of cod, haddocks, and flounders at 

 St. Andrews. In re-entering the sand the animal reverses its position in the tube, 

 makes a battering-ram of its tentacles, which are twisted into a conical mass, and aided 

 by the " Lippen-organ " soon introduces the end of the tube, and enables it to be screwed 

 into the sand. 



Mr. Arnold Watson observes that the imbrication of the constituents of the tubes was 

 not so noticeable in the Neapolitan examples, which were chiefly covered with fragments of 

 black material not sufficiently thin and flat for this purpose. 



Considerable variety occurs in the structure of the tubes. Thus in some, fragments of 

 the spines of echinoderms, chiefly of Spatangoids, of the tests of heart-urchins, pieces of the 

 tubes of Ditrypa, and fragments of Balani are found. Remarkably coarse tubes came from 

 40 fathoms off Bantry Bay, where the bottom is evidently composed of broken shells. 



The tubes of those dredged at 640 fathoms by the < Knight Errant ' are largely 

 composed of Grlobigerinae and sand-grains, besides being hirsute with sponge-spicules which 

 entangle mucus. The posterior end of the tube is coated with the extraneous organisms, 

 only the conical anterior end being free. Sometimes the tubes are white and long, as in 

 4 to 5 fathoms off Balta (J. G. Jeffreys). A tube, fully six inches in length, occurred between 

 tide-marks at Lochmaddy, North Uist, and of a variegated hue, hornblende being mingled 

 with fragments of white shells, whilst the inner lining was dense. In this case the tube is 

 narrow and long, and the imbricated condition of the external coating is less typical. 

 Unfortunately no tentacular crown is present in the specimen. 



Young forms use finer particles, and their tubes are sometimes proportionately long 

 and narrow. 



Accompanying the tubes of Owenia, covered with translucent sand-grains and 

 Foraminifera, in the ' Valorous ' Expedition of 1875, was a cylindrical growth of Aleyonidiwm, 

 which closely resembled such a tube, even to the slightly tapered ends. 



Reproduction. — The sexual elements are developed as usual, viz. on the branches of 

 the ventral blood-vessel, and shed into the coelomic space. Their escape from the body- 

 cavity was supposed by Grilson to be by the epithelial canal on the dorsum of the second 

 abdominal segment (sixth), but Arnold Watson discovered that in May both male and 

 female elements are discharged by two pores to the right and left of the vent — a portion of 

 the posterior end of the body in the males projecting from the anterior aperture of the tube. 

 The ova are enveloped in a gelatinous mass placed near the tube. As in the Nemerteans 

 the stimulus of the emission of sperms is sufficient to cause the females to deposit their 

 ova. The anal pores through which the ova are discharged have their walls lined with 

 cylindrical transparent cells, which may secrete the gelatinous substance. 



In an example dredged by the ' Knight Errant ' in 640 fathoms, at Station 8 (Atlantic ?) 

 the perivisceral cavity contained many large ova about the size of the Globigeringe on the 

 wall of the tube, but of a yellow colour. 



Mr. Watson followed the development of the ova to the Mitraria-stage. On the 



