308 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



occupied when the worm was young and little being- bitten 

 off by its jaws, when it finds the aperture becoming 

 inconveniently small. This view is supported by an 

 instance of shortening of the tube actually seen in 

 Onujjhis concliilega, to which reference will be made later ; 

 and it is further confirmed by the fact that frequently 

 HyaMncecia tubes bear clear internal evidence of this 

 having taken place, since, as the tube is lengthened, the 

 old valves are removed and reconstructed in new positions, 

 traces of the old valves often being left permanently on 

 the walls of the tube. Specimens in my possession thus 

 show clearly that the present site of the hinder (alternate) 

 valves was once occupied by the front (opposite) valves 

 made by the younger worm. 



Although the tube itself is undoubtedly formed simply by 

 secretion poured out direct from the body of the worm, the 

 internal valves (v, v', fig. 1) which guard it are produced 

 in a very different manner. They are a later production, 

 most skilfully constructed by the worm. Their thicker 

 portions attached to the walls of the tube are probably due 

 to the action of the jaws, palps and mouth parts, aided 

 possibly by the fore feet of the animal, manipulating 

 material obtained from the coating of the tube, or even 

 from old valves, which is worked up for the purpose in 

 the mouth of the worm ; while the delicate free mem- 

 branous edge of the valves may be formed by direct 

 secretion, like the tube itself. The experiments upon 

 which this opinion is based require further confirmation. 

 but they are briefly as follows : — 



Two healthy specimens of Hyalijioecia, which had 

 become acclimatised in my aquaria, were selected, and at 

 different times (a few days apart) the portion of each tube 

 containing the valves at the wider end was cut off, without 

 injury to the worm. Tn a short time the worms, on both 



