from the Xurlh Sea and adjacent parts. 313 



arc forcibly pressed or cut 0|)eii. Arnold Watson says that 

 the valve at the anterior end is V-shapcd, and this I find to 

 be correct in all the tubes of this collection. Sometimes, 

 however, this anterior valve may be double, and where this 

 is so the valves do not appear so strong and tough as \vheu 

 they are single — that is, when there is only one pair present, 

 for each valve is composed of two parts. The posterior 

 valve, however, varies in shape, and in many adults is seen 

 as a series of single valves which form one large zigzag 

 valve (PI. XVI. figs. 5-G). In some (and especially young) 

 forms it appears as a double V-shaped valve, similar to that 

 found in the anterior region of the tube (PI. XVI. fig. 4). 

 The double V-s!iaped valves are very thick and much more 

 opaque than the rest of the tube and other valves. The 

 valves, as Watson remarks, are no doubt for protection and 

 are automatically closed by the inrush of sea-water. If 

 there were no valves the animal would be open at front and 

 rear to attacks from its enemies, and although it might be 

 able to defend itself from frontal onslaughts, yet from attacks 

 in the rear it would be defenceless, owing to its inability to 

 turn in its tube and owing to the stiff'ness of the tube itself. 

 Possibly this is why the valve system at the posterior end is 

 much more complicated than at the anterior end. As 

 AVatson and others have ascertained from living examples 

 kept in captivity, the tubes are elongated at the anterior end 

 as the animals grow. Again, Izuka remarks on the thinness 

 of the anterior in comparison with the posterior end, but 

 this is due to the former being lengthened, while the latter 

 is thickened and strengthened. The tuljcs are V-funncI- 

 shapcd, the anterior opening being much larger than the 

 posterior one, and in adult specimens and often in fairly 

 lai'ge young forms the tubes are beautifully ornamented, the 

 ornamentations being the marks left by the pre-existing 

 valves, which are removed by the animals when they increase 

 their tubes. Watson, moreover, found from his experiments 

 that the animals could renew and even replace the valves 

 when damaged or cut oft'. However, when the valves are 

 entirely removed more than once, the animals take longer 

 each time to replace them, and often the task is too great 

 and proves fatal. It is said that a tube can be secreted in a 

 day, but Watson found that it took twelve hours to repair 

 the damage done to the valves alone. In the young forms 

 the valves and tubes are very thin and quite transparent. 



As regards reproduction, many ripe females were taken iu 

 the month of June, but no ripe males occur. The ova arc 

 fairly large,, 0-21. mm. {De St. Joseph), have a porous zona 



