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These last, as a compound of several united Amoebae, would 
only have the advantage of growing quicker and becoming 
stationary sooner than the single Amoebae. To complete the 
natural history of the Protomyxa, it still remained only to 
observe the encysting of the adult form, the transition from 
the free-moving plasmodia to the stationary red balls which 
had attached themselves to the Spivula-shell near the latter. 
I succeeded in establishing this also. Two of the largest of 
the best-fed plasmodia, which contained very numerous 
vacuoli, and which had formed a very extended sarcode net, 
with many branches and anastomoses, after some time began 
to slacken their extremely rapid currents, and to simplify 
their pseudopods. The siliceous shells of the many absorbed 
Diatomaceae were rejected, and the branches and twigs of the 
pseudopods were successively retracted. At last they drew 
back the main stems, which had ’every where become simple, 
into the central plasma-body, and the entirely homogeneous 
sarcode body took the form of an irregular lump, and finally 
rounded itself into a regular ball. 
Now commenced the separation of the covering of the 
cyst, in which the sharply defined single outline of the 
orange-red plasma-balls passed into a perceptible, though 
certainly fine, double outline. A second, and then a third, 
concentric boundary line soon followed this, and then the 
proper concentric hyaline cyst-covering appeared somewhat 
quickly (in the course of a day), its layers corresponded with 
the stated breaks of the separated gelatinous skin. At 
first a quantity of vacuoli were still perceptible in the 
plasma during the encysting process, which appeared and 
disappeared here and there, but visibly decreased in num- 
bers ; and after the complete development of the cyst-cover- 
ing no vacuoli could be any longer perceived in the orange-red 
plasma, now interspersed with numerous granules. The en- 
cysted plasma-ball was now no longer to be distinguished 
from those red balls whose transition to the mass of sporules 
I have above described. Thus was the cycle of the genera- 
tion of the Protomyxa completed, and the course of its simple 
and remarkable life-history established. Protomyxa auran- 
tiaca is a Moner which, like the Vampyrella and Protomonas , 
appears in two different conditions during the course of its 
individual life. In its free-moving condition the Protomyxa 
appears as a naked Gymno-moner, of the morphological im- 
portance of a Plastidien (cytode), as simple as can be con- 
ceived, which successively assumes three different modifica- 
tions : — I. The swarming flagellate condition, a free swim- 
ming, naked, tailed, pear-shaped, sporule (fig. 5). II. The 
