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thick walled cell, and it immediately begins to increase in size 
and assume a more rounded outline. The subsequent changes 
lead up to the formation of what I regard as resting spores. The 
yellowish-brown colouring matter which is at first diffused 
throughout the body becomes concentrated in the nucleus, the 
latter then assumes a brilliant red colour : afterwards the nucleus 
undergoes division, and either one or two orange-coloured spores 
are formed, at the expense of the granular protoplasmic contents, 
which gradually disappear as the spores increase in size. Unfor- 
tunately I have not been able to ascertain what takes place after 
the spores are fully formed, the specimens which I had under 
observation having all remained in the same condition for the 
last two months. The cell wall appears to resist the attacks of 
the bacteria and infusoria, which exist in vast numbers in the 
vessel containing them. 
This species made its appearance during the month of March 
last in such vast numbers as to render the water in Port J ackson 
quite red, and for a period of six weeks the whole of the surface 
water was more or less discoloured by the presence of this minute 
organism. When viewed from a distance, the surface of the 
water presented a variegated appearance, consisting of long 
streaks and patches of glaueus-green, yellowish-brown, and blood- 
red colour. The various streaks of red changed about from time 
to time owing no doubt to the direction of the wind and tidal 
currents. In nearly all the bays and small inlets the water on 
the surface was quite thick with the organism, and if a bottle 
full of water was taken up and allowed to stand for a few minutes, 
there was a thick brown deposit formed at the bottom, consisting 
of the bodies of the Glenodinium. 
Port Jackson, March, April, and May, 1891. 
Family Gymnodinida, Bergh . 
19. Gymnodinium spirale , Bergh, l.c., p. 223, pi. 16, f. 70-71. 
Kent, l.c. p. 858, Appendix. Biitschli, l.c. pi. 51, f. 5. (Plate 
xxviii., fig. 8.) 
During the months of April and May, this species was obtained 
in abundance by dipping a tube into the water. To my mind it 
appeared to be just as plentiful as the Glenodinium , but owing 
to its being transparent it did not perceptibly influence the colour 
of the water. 
Hunter’s Hill, Mossman’s Bay, Woolloomooloo Bay, and Middle 
Harbour. 
Class RHYNCHOFLAGELLATA, Lankester . 
Family Noctilucid^. 
20. Noctiluca miliaris , Suriray ; Kent, l.c., p. 397, pi. 1, f. 33-34. 
It is with some hesitation that I venture to record this species. 
So far, I have not seen the flagellate form. The stationary form 
