198 Proceedings of the Royal Physical Society. 
one into the other, according as the protoplasm comes into contact with the 
external surroundings; nucleus, one or more; and contractile vacuole. 
The differences, apparent or accidental, seasonal or pathological, are to 
be found in the granular condition of the plasma; the contained crystals ; 
the appearance of the nucleus, together with the food-supply, habitat, and 
method of reproduction. 
General appearance and granular condition of protoplasm, ete—The 
granulation is shown in different degrees by the three types; A. proteus X 
showing the least, and A. proteus Z the greatest, degree. 
In general appearance A. proteus X may be recognised not only by its 
freedom from an excess of granules, but also by the translucent limpidity 
which pervades it; by the easy mobility of the whole organism and by, what 
impresses one most, its glorious living when in a healthy condition and 
a happy environment. Its size is 200y-350y. Its large crystals have 
already been alluded to, and these together with its clearness, suggestive of 
depth, purity, and freshness of habitat, combine to make it by far the most 
beautiful of the three forms of A. proteus under discussion, fully meriting the 
“admirande simplicitas animal” of Pallas.t Its food, as stated, consists very 
largely of diatoms, when these are obtainable, but not by any means only 
diatoms; hence a suggestion that change of diet combined with environ- 
ment may produce A. proteus Y. This I have not yet proved to my own 
satisfaction. 
Whether this be so or not, it is of interest to note that the supply of 
A. proteus X, from a pond which for two years had produced this type in 
abundance, with the rarest possible appearance of Y or Z, suddenly ceased, 
for no specific reason, and within a few months while no more A. proteus X 
could be obtained, both A. protews Y and A. proteus Z were forthcoming in 
very respectable numbers. Now, however, it is impossible to obtain Ameba 
proteus of any “type” from this formerly plentiful source. 
A. proteus Y is, as a rule, larger than A. proteus X, but not always so, 
300 »-500 », and in éxceptional cases more. Its protoplasm is usually 
very granular, as indicated by the names given to it by observers, but there 
is a gradation, the granular condition increasing while the whole amceba 
inclines to the dusky tinge as the individual amcebe approach the Z end 
of the series (Fig. 3). 
A. proteus Z is, generally speaking, very large; small members in the 
multinucleate condition may be found, but they are not common. The 
largest I have found measured some 1000», and when it lengthened out for 
division reached a measurement of 1500». The granulation is similar to 
1 Pallas, Hlenchus Zoophytorum, 1766, p. 417. 
