564 EEPOET — 1891. 



worm is only an accompaiiiment, and not the cause, of the 

 disease. An excellent ctescription, with illustrations, of the 

 worm, Lcucodorc ciliata, together with an account of the 

 phenomena attending its existence in the oyster-shells, has 

 been prepared by Mr. W. T. Whitelegge, of the Sydney 

 Museum, for the New South Wales Fisheries Commission; 

 the view favoured in that pamphlet being that it is the direct 

 cause and propagator of the disease. 



Le7icoclore is not a newly-discovered species. It was first 

 described as a British species so long ago as the year 1838, and 

 has been found to be practically cosmopolitan in its distribu- 

 tion. The habitat ascribed to it by Dr. Johnston, in his 

 "Catalogue of Non-parasitical Worms," 1865, is as follows: 

 " Found living between seams of slaty rock near low- water 

 mark, and burrowing in the fine soft mud which lines the 

 fissures." I have been recently informed, by an experienced 

 and highly observant oyster-grower, that the same species of 

 worm was noticed by him many years ago burrowing in the 

 mud-filled crevices of timber-work in Sydney Harbour. The 

 species, like other members of its class, is an essential mud- 

 lover; and its natural instincts guide it in its earliest embryonic 

 days to seek out and settle down in a congenial mud-lined 

 cradle. 



Turning to the conditions accompanying the appearance of 

 the disease in New South Wales, as described by Mr. White- 

 legge, much evidence is found that supports the interpretation 

 I am disposed to advocate. He remarks that "the principal 

 home of the worm appears to be on the mud-flats about low- 

 water mark. The oysters from this region were invariably 

 infected with the worm, particularly those which lay loose 

 on the surface, or were partially buried in the mud. Those 

 oysters which w^ere fixed to some solid substance, and elevated 

 ever so little above the surface of the mud, were comparatively 

 free from the pest." This testimony goes far to show that this 

 so-called worm disease is essentially a " dirt disease." It is only 

 in a muddy environment unsuitable for the healthy growth of 

 the oyster that it spreads ; and that it is the mud that attracts 

 the worm, and not the oyster per se, is demonstrated by the fact 

 attested to, that the oysters elevated but a few inches above 

 the muddy stratum are relatively free from the affection. The 

 primary cause of the disease has yet to be fully determined, 

 and it is a subject of high importance to all oyster-growing 

 communities. The rock-oyster, Ostrea glomerata, affected by 

 the disease, is, as previously remarked, a species that attains 

 to its maximum development in brackish water, and, indeed, 

 survives exposure to fresh-water immersions in times of floods 

 that would prove fatal to the so-called mud-oyster, Ostrea 

 edulis. As a corollary to these brackish- water proclivities of 



