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— which is the cause of the discolouration of the water — on fish 

 and other organisms. Tlie effect on the shore fauna has been 

 very destructive ; I tind that the oysters, mussels, and other 

 bivalves have been nearly all destroyed. At all the places I 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 are 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. During my examination 

 of the shore I searched carefully for fish, but failed to find any 

 dead ones, nor could I 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 aljsence of the usual 

 forms which live under stones, such as worms, ascidians, starfish, 

 polyzoa and zoophytes — all seem to have suffered more or less. 



The question as to how this vast destruction of shore life has 

 been brought about is a rather difficult one to decide, and could 

 only be satisfactorily determined by direct experiment in a well- 

 appointed biological laboratory. I, 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 I 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 niay 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 " Encyclopjcdia Britannica," IJth edition, Vol. xix., p. 859, is 

 given to show that the composition of these organisms is very 

 similar to that of diatoms, desmids, ttc, which are known to 

 constitute a highly nutritious food for tish, oysters, and other 

 forms of animal life : — " The Dinofiagellata are either enclosed in 

 a cuticular shell (Ceratium, Peridinium, Dinophysis, Diplopsalis, 

 Glenodinium, Prorocentrum, etc.) or naked (Gyuuiodinium and 

 Polykrikos). The cuticular membrane (or shell) consists of 

 cellulose, or of a similar substance (cf. Labyrinthulidea), and not, 

 as has been supposed, of silica, nor of chiton-like substance. 



