230 SABBLLA PENICILLUS. 



after preservation -^ inch, and it had about sixty-six segments. The first two 

 bristle-tufts are somewhat short, the third to the sixth are long, and these corresponded 

 to the first region of the body ; consequently only five pairs of dorsal hook-rows are 

 present. The seventh pair of bristle-tufts is slender and small, so that the outline is 

 narrowed, the adjoining tufts being longer. Toward the tip of the tail elongated, slender 

 simple bristles occur as in the adult. The bristles correspond in arrangement and 

 structure with those of the adult. The anterior hooks differ in having a shorter 

 posterior basal process, but they are accompanied by the same paddle-shaped bristles. 

 The anal segment is bilobed, and has a peculiar series of dark pigment-specks. 

 Four pairs of setigerous processes bearing short bristles occur behind the last hooks, 

 which are small and only three in number. The bristles increase in length at the 

 sixth from the tip. The opaque glandular tissue splits at the termination of the 

 rows of dorsal hooks at the second ring from the latter, since the first has a bar 

 obliquely bevelled at the lower edge. The splitting continues to the tip of the tail and 

 gives a regular arrangement to the parts. Both anteriorly and posteriorly the bristles 

 commence before the hooks. Four pairs of bristles occur before hooks appear, 

 the first hooks being between the fourth and fifth bristle-tufts, and their bases 

 are undeveloped. The first five pairs of bristles are short, but the sixth are decidedly 

 longer. 



Reproduction. — Lo Bianco (1909) found that at Naples the rose-coloured ova were 

 deposited in April. At St. Andrews ova occurred in the coelom in October. 



Parasites. — M. Sars found a parasitic Copepod on this form, viz. Sabelliphilus elon- 

 gates. The body is elongated, somewhat rounded, attenuated posteriorly, and has ten 

 segments. In the female the head is fused with the first thoracic segment, but in the 

 male it is separate. Rostrum bifurcate. First pair of antennas with seven articulations, 

 the first two in the female much dilated, in the male less dilated. A second pair of 

 antennas quadriarticulate, the terminal joint with three hooks and the penultimate with 

 one hook. Maxillipedes triarticulate, terminal joint with a hook. First four limbs 

 triarticulate, fifth rudimentary, simple, uniarticulate. Ovigerous sacs elongate, 

 subcylindrical. The same parasite occurred in examples from St. Andrews and the 

 West Coast of Ireland, and in both cases attached to the left edge of the branchiae at 

 the dorsal fissure. 



Habits. — 8. penicillus is fond of a muddy bottom at some depth. "When sickly it 

 leaves its tube, apparently for better aeration. It is most active at night, and is exceedingly 

 shy and sensitive. The posterior end, like the anterior, can be regenerated. Thus in 

 a large example (Plate CXX, fig. 5) the new segments form a conical appendix with a 

 streaked purplish spot of pigment near the tip. 



The tube may reach the length of 2 feet, and is fixed to stones on the bottom. The 

 elasticity of the distal end closes the aperture, the rest of the tube being composed of 

 secretion and mud, and so smoothly rounded as to resemble a tube of caoutchouc (Dalyell) 

 of considerable firmness, and some are nearly f- inch in diameter. Many are coated 

 with patches of, or entirely sheathed in, Alcyonium digitatum, so that the tube must stand 

 more or less erect, and have free aeration. In connection with the muddy surroundings 

 from which the animal forms its tube, further light is thrown on the azoic-mud theory of 



