114 THE WORM DISEASE IN OYSTEHS. 



side inwards tliey are longer and more tubular ; but tbis is owing to the 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 which is affected, tjltimately 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, hecoming shallower inwards and ceasing 

 to he grooved at all. 



The Remedy. 



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

 their destruction. Those I experimented on in various ways during a period 

 of two months, 1 have had under observation 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 oysters appeared to be in a healthy condition. 

 Some which were kept in an extempore aquarium for over two months, were 

 cultivated until t,he whole of the worms had died out. This I attributed 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 worms. But this 

 method has its drawbacks from the dilficulty of transporting them over long 

 distances, and could only be used in favourable localities. The most effective 

 as well as the quickest method would be the drying process. The oysters 

 should be removed from the beds, freed from mud by washing, and then 

 placed under a shed or cover of some kind, to protect them from the sun's 

 rays. The oysters should be spread out in thin layers, and occasionally 

 turned over, so as to ensure the thorough drying of the shells externally. 

 The process may be continued for ten days or longer — if the oysters would 

 stand it. They might afterwards be relaid on the beds, if suitable ground 

 exists on which to lay them — that is to say ground having a stony or shelly 

 bottom. If they are laid on a mud surface, they will very soon be infested 

 again. Another method which might be useful would be to remove the oysters 

 into prepared ponds, into which none but moderately clear water is allowed 

 to enter, or place them on a sandy or pebbly beach in such a position that 

 they would be exposed to the sun, and get partially dry between every rise 

 and fall- of the tide. No doubt if either course was adopted and continued 

 for some months, the worms already in the oysters would be destroyed. The 

 above mentioned remedies can only be applied to oysters that are loose or 

 attached to small objects, such as shells, <&c. 



So long as oysters are cultivated on the bare surface of the mud, they will 

 be liable to the attacks of the worm ; but if some solid substratum be provided 

 for the spat to fix upon, and so remove them from direct contact with the 

 mud, the oysters will have a chance of escaping the disease. 



As far as I can ascertain, nothing has yet been published in reference to 

 the eggs of the worm, and the following, if new, may be of interest : — The 

 ova appear to be matured in the body of the worm and commence on about 

 the thirtieth segment. Each succeeding segment to about the fiftieth bears 

 a pair of egg-sacs, each of which contains between fifty and sixty eggs. The 



