— which is the cause of the discolouration of the water — on iish 
ami other organisms. The effect on the shore fauna has been 
very destructive : I find that the oysters, mussels, and other 
bivalves have been nearly all destroyed. A tall the places T have 
visited, from Hunter’s Hill, on the Parramatta River, down to 
Watson's Bay, the bivalves are killed, and at Little Sirius Cove 
the limpets and periwinkles arc? lying about with the animals still 
in the shells, mostly in a state of putrefaction ; the stench from 
the bed of mussels is almost unbearable. 1 Hiring my examination 
of the shore T searched carefully for iish, but tailed to hud any 
dead ones, nor could T gain any information of any having been 
seen floating about in a dead or dying condition. The effect on 
the other kinds of life besides the mollusca has been very destruc- 
tive, and there seems to be almost a total absence of the usual 
forms which live under stones, such as worms, ascldians, starfish, 
polyzoa and zoophytes — all seem to have suffered more or less. 
The question as to how this vast destruction of shore life lias 
been brought about is a rather difficult one to decide, and could 
only he satisfactorily determined by direct experiment in a well- 
appointed biological laboratory. 1, however, submit the following 
as the result of my investigations in the matter, and in doing so 
I wish it to be distinctly understood that the conclusions are put 
forward tentatively, as a reasonable explanation of the phenomena. 
In the first place, there cannot be the least doubt but that the 
Peridinium appears regularly each year in larger or smaller 
quantities ; and T have been assured by various people that this 
discolouration of the water has been noticed on many occasions 
from 1856 down to the present time. But why has it appeared 
in such vast numbers during the last few weeks ? It is highly 
probable that all the conditions favourable, to its development 
have been nearly perfect, and the influences which might act 
injuriously have been reduced to a minimum. The very large 
rainfall may have affected the salinity of the water favourably, 
and the lengthened period of calm weather which has prevailed 
since its appearance might also contribute to its development. 
From what is known of the chemical composition of the Peridinia 
there is no reason why they should be regarded as injurious food 
for fish or any other organisms. The following account from 
the “Encyclopaedia Britannica,” 9th edition, Vol. xix., p. 859, is 
given to show that the composition of these organisms is very 
similar to that of diatoms, desmids, &c., which are known to 
constitute a highly nutritious food for fish, oysters, and other 
forms of animal life : — “ The I )ino flagella ta are either enclosed in 
a cuticular shell (Ceratium, Peridinium, Dinophysis, Diplopsalis, 
Glenodinium, Prorocentrum, &c.) or naked (Gy mnodi ilium and 
Polykrikos). The cuticular membrane (or shell) consists of 
cellulose, or of a similar substance (of. Labyrinthulidea), and not, 
as has been supposed, of silica, nor of cliiton-like substance. 
