180 



quantities. At Coogee, Maroubra, and the outer Ijeacli at Manly, 

 I failed to obtain specimens in watei* taken direct from the sea, 

 but I found them fi'equently in rock-pools. My visit to Middle 

 Harbour was made in a waterman's boat which started from 

 Long Bay. During the trip I examined many of the smaller bays 

 and also the water round about the mangrove flats. At the time 

 of my visit the organism was not abundant, but there was ample 

 evidence to show that it had been there in quantity from the 

 fact that many of the oysters had been killed; in the lower parts 

 of Middle Harbour a large percentage of the oysters were seen 

 with the valves gaping widely and the animals gone, or in a high 

 state of decay, whilst those towards the head of the harbour 

 seemed to be unaffected. So far as the harbour proper is con- 

 cerned, I found that the oysters and mussels with few exceptions 

 were destroyed, and it was a difficult matter to obtain living 

 specimens for examination. Abundant evidence of the destructive 

 influence of the organism on the oysters, mussels, and other 

 bivalves living within tidal limits was plainly vi.sible on the 

 piles of the jetties and along the shores from Manly to the head 

 of Tarban Creek. The rest of the shore fauna, consisting of 

 limpets, the various species of univalves, starfish, worms, ascidi- 

 ans, and other lower forms of life, was all more or less seriously 

 affected, and the dead and the dying were strewn about in great 

 profusion. As a consequence nearly the whole of the higher 

 forms capable of rapid movements had retired to deep water. 



Some of the places wliere I have been in the habit of 

 visiting, and which under normal conditions were literally 

 swarming with life, seemed to be almost deserted. After turning 

 over the stones the only living forms met with were a few worms, 

 one of which, Fhymosomajuponica, appeared to be unaffected. 

 The Crustacea and small fish usually so plentiful were entirely 

 absent. As far as I am able to judge, fully one half of the 

 sliore fauna must have been destroyed, and the bivalves almost 

 exterminated, at least such was the case in those localities where 

 the organism was abundant during the whole of the visitation. 

 The great destruction of life brought about by such an apparently 

 insignificant organism, is of the highest interest from a biological 

 point of view, as shewing our limited knowledge concerning the 

 causes which influence our marine food supplies. This is 

 particularly the ca.se in regard to the cultivation of the oyster, 

 for there are many cases on record of its almost total disappearance 

 from localities which foi'merly yielded abundant supplies,* without 

 any satisfactory reason being given. The facts ascertained in 

 connection with this somewhat mysterious visitation may possibly 

 throw light on the matter, for no doubt the presence of similar 



* See Prof. Huxley's paper in the English Illustrated Magazine, 1883 

 (November), pp. 115-121. 



