■85 
Observations on the Pyrocystecc. 
Amylum-bodies. In all the four species above mentioned, 
there are often to be found a number of clear refractive bodies of a 
spherical oval or rod shaped form They are fairly often to be 
seen in P. fusiformis, but the most striking case observed was that 
of P. lunula, where on one occasion they were seen to fill nearly 
the whole cell, hiding from view most of the protoplasm (fig. 8). In 
l\ hamulus, the granules are usually of small size, but sometimes 
in this species also they occur in such numbers as to obscure the 
protoplasm (fig. 7); in P. pseudo no ctiluca also, as mentioned earlier, 
the bodies are sometimes found, but only in small numbers. The 
bodies are not of a proteid nature, for with osmic acid they 
give no reaction; but their behaviour with iodine is peculiar. With 
a fairly strong solution of iodine in potassium iodide, they take on 
at first a deep brown colour, which soon becomes almost black ; if 
when in this condition they are washed with water, they lose part 
of their colour and become of a reddish-purple tint. At the same 
time they swell up under the action of the water, and show a 
differentiation into a peripheral more dense part and a central 
apparently more watery part. Their exact nature must, for the 
present, remain uncertain, but they are probably to be classed with 
the so-called Amylum-bodies which have been observed in a few of 
the Peridineas. Whether either they or the numerous oil globules 
which are always present have any reason to be considered as 
an assimilation product of the chromatophores, is an interesting 
question which cannot yet be answered. 
The systematic position of the Pyrocystecc .—On the first 
discovery of P. psendonoctiluca and P. fusiformis it was believed 
that their wall contained silica, and they were therefore classed by 
John Murray (6) with the Diatoms. When this view was given up 
later, and the wall shown to consist of cellulose, Murray (7) put 
forward no further view as to the affinities of the genus. 
A number of zoologists have, however, for some time, considered 
P. pseudonoctiluca to be merely an encysted condition of Noctiluca. 
Saville Kent (4) was the first to put forward this theory, but it owes 
its support to the distinguished authority of Biitschli (1). This 
observer states that, after the examination of some material supplied 
to him by John Murray, he must support the view of Saville 
Kent. He bases his view on the belief that no cell-wall is present, 
and that there cannot be a siliceous sheath, for no trace of it is left 
after the action of strong sulphuric acid. That no siliceous wall is 
present is very true, but how Biitschli came to overlook the presence 
