114 
pocla, Myxomycetse, &c. They are also not true contractile 
vesicles such as occur in the true Infusoria (Ciliata), and 
in some Amoebae ( e.g ., A. quadrilineata). These latter are dis- 
tinct and permanent organs, no matter whether they can be 
perceived to have an essential wall or not. True contractile 
vesicles always occupy precisely the same situations in the 
body, while the vacuoli appear and disappear here and there 
in the solid albuminous mass of the plasmaparenchyma. 
From this definition of vacuoli as distinguished from con- 
tractile vesicles it is naturally in no way disputed but that 
transitional intermediate forms between both occur. On 
the contrary, I consider it very probable that the contractile 
vesicles are developed from simple vacuoli phylogenetieally 
(by natural selection). 
The vacuoli, as well as the red granules which are scattered 
in the homogeneous plasma of the Protomyxa and lie every- 
where and wander everywhere, are appearances which stand 
in the closest relation to the change of substance (StofFwechsel) 
of this Moner. I tried to keep the Protomyxa in shallow 
watch-glasses with sea- water and succeeded, with the best 
results. 1 placed the small watch-glasses, each of which con- 
tained a single Protomyxa, in a larger glass filled with water, 
and inverted a large glass over it, so as to form a very roomy, 
damp chamber ; and in this manner I succeeded in keeping 
the Protomyxa alive more than three weeks, and in observ- 
ing the phenomena of their nourishment and reproduction 
in full detail. The next fact which I ascertained by con- 
tinual daily observation was that the number of the vacuoli 
and of the red granules was in direct proportion to the quan- 
tity of food taken. I kept some Protomyxse in pure sea- 
water without food, while I supplied others with plenty of 
Diatomacese for food. In the first, the number of the red 
granules as well as of the vacuoli had, after a few days, 
already perceptibly diminished, while in the others they 
continued the same, and from better nourishment even 
increased. The individuals which were best fed with dia- 
toms were quite filled with red granules, so that the sarcode 
was thickly clouded ; and the middle yiarts of the body espe- 
cially appeared quite opaque. Presently a greater number 
of larger and smaller vacuoli appeared on all the edges and 
extremities. On the other hand the hungry individuals 
were pale, more yellow than red coloured ; the number of 
red granules had remarkably diminished, as well as the num- 
ber of vacuoli, and finally disappeared entirely (comp. figs. 
11 and 12). 
It is plain from this that the granules scattered in the sar- 
