49 



that it is worn away. If the worm has been long in the shell, the 

 grooves formed are deep, and the longer they remain the deeper 

 they become. When measured from the outside inwards they are 

 longer and more tubular'; but this is owing to tlie fact that the 

 growth or increase in the size of the shell forces the entrances 

 further outwards and upwards, or downwards, as the case may 

 be, according to whether it is the upper or lower valve wjiich is 

 affected. Ultimately the openings have the keyhole-like aspect 

 which look as if they had been bored, but which, if carefully 

 examined, will show that they have passed through the various 

 phases before mentioned, becoming shaUotver inwards and 

 ceasing to be grooved at all. With regard to the worm boring 

 into limestone, shale, Ac, mentioned by Englisli writers, I 

 think it is quite possible that a young worm may take possession 

 of a small depression, and as it grows gradually enlarge it by 

 its constant movements in and out, until it has formed its 

 tube in the same Such tubes may serve for a succession of 

 generations, being still increased in size by each occupant, as is 

 the case with some of our sea-urchins which form holes in the 

 sandstone of Port Jackson. But still there would be an absence 

 of boring in the sense used with reference to this worm. Pro- 

 fessor Mcintosh, in the Ann. and Mag. of Nat. Hist., vol. 24, 

 ser. 1868, p. 278, speaks of its boring into any shell that is thick 

 enough to be bored. 



The Remedy. 



There are several ways in which to deal with the worms, with 

 a view to their destruction. Those which I am about to give are 

 the result of direct experiment, and if carried out in a proper 

 manner, will prove effectual. When I returned to Sydney, after 

 my fortnight's sojourn at Newcastle, I brought Imck a large 

 quantity of diseased oysters. These I experimented on in various 

 ways during a period of two months, having them under obser- 

 vation daily during the whole of that time. Some of the worst 

 cases were placed in fresh water, which had the effect of killing 

 the worms and some of the oysters ; the latter were no doubt 

 killed by the putrescent germs developed in the mud after the 

 death of the worms. Others which were kept without water for 

 fourteen days, were afterwards placed in salt water for several 

 days, and in all cases the worms were destroyed, whilst the 

 oystei's appeared to be in a healthy condition. Some which were 

 kept in an extempore aquarium for over two months, were 

 cultivated until the whole of the worms had died out. This I 

 attribute to the water supplied, not on account of its being bad, 

 but from the fact that it was moderately clear and free from 

 mud, which seems so essential to the life of the worm. 



From the above series of experiments we may conclude that 

 placing the oysters in fresh water for a few days will destroy the 



