180 
quantities. At Coogee, Maroubra, and the outer beach at Manly, 
I failed to obtain specimens in water taken direct from the sea, 
but I found them frequently 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 visible 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 where 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, Phymosoma japonica, 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 
shore 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 case in regard to the cultivation of the oyster, 
for there are many cases on record of its almost total disappearance 
from localities which formerly 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 J s paper in the English Illustrated Magazine, 1883 
(November), pp. 115-121, 
