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become somewhat clearer upon the surface and evidently 
a process of differentiation goes on by means of which a very 
delicate investing membrane is formed, but it is so delicate 
that it can only with difficulty be seen; and, in fact, can 
hardly be said to exist asa separate membrane. But upon 
one side is now seen to appear a bulging outwards of the 
mass until a nipple-like protuberance is formed which 
however is not filled with the green matter formed elsewhere, 
but is clear and colorless. I have noticed that in most cases 
this protruding portion is formed at the point just opposite 
to the place in the cellulose cell-wall of the filament from 
which the spherical body has just escaped. But as this is | 
not invariably the case it can hardly be considered as any- 
thing more than accidental. Soon thereafter, there is seen to 
be a slight agitation going on upon the surface of the sphere, : 
near to, and upon one side of the clear space. This moye- 
ment then assumes a more definite character, and at last a 
moving cilia is seen to be formed or differentiated from the 
outermost portion of the globe. Soon another and another 
are formed in the same manner, attached by their bases 
around the clear space, and soon, that is to say in fifteen or 
twenty minutes, a ring of active ciliw are seen to surround 
the nipple-like projection. As soon as they have all made 
their appearance immediately they all begin to move together 
and in a violent manner, so that motion is imparted to the 
whole mass, and it swims about actively through the water. 
And this motion is so active that it is often difficult to follow 
the mass, and keep it within the field of the microscope. For 
several minutes or, more rarely, for half an hour, this motioa 
goes on, and up to this point I find that these changes have 
been observed and recorded by others. But now comes what I 
consider the most important part of this history. 
It can be readily understood that, on account of its 
violent action, the further history of the spherical mass could 
not easily be followed, but fortunately on several occasions 
I saw specimens entangled in a mass of filaments in such a 
way that they could not escape from the field of view. 
Then I saw that the motion became gradually less and less 
