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vigorous and at the same time the cilize disappeared. one by 
one, melting out of view, being apparently absorbed 
again into the mass from which they were originally de- 
veloped. At the same time one of them seems to elongate 
until it is one to three times as long as the diameter of the 
spherical mass, and also, its point of attachment changes until 
we find it springing from the centre of the clear projection. — 
While this is going on, the whole mass, not changing its 
position, assumes however, a totally different outline. That 
is to say, the clear nipple-like blunt part remains about the 
same, but the opposite portion becomes pointed, while the 
intermediate space is inflate in such a way that the whole 
creature in outline somewhat resembles a trefoil clover. The 
inflated part, however, does not remain rigid, but soon sub- 
sides, while the clear end becomes more’ pointed, and now 
the creature is spindle-shaped in outline. As there is now 
but one cilium it is by means of it that the creature moves 
about in an extremely active manner. In some, and in fact 
in by far the most cases I observed, the swelling of the 
middle portion is not fixed but moves down the length 
of the creature towards what may with some propriety be 
termed the posterior extremity, as it is always projected 
backwards when it is moving through the water, and there 
disappears to be soon followed by another swelling and 
wave-like projection and so on. In fact, an action resem- 
bling very closely that seen to take place in the intestines 
of animals, and known as peristalsis, takes place. Many 
individuals move directly and straight onwards, preserving 
their body perfectly rigid, so that after a time the cell-con- 
tents are seen to arrange themselves in longitudinal bands. 
Others, again, revolve on their longest axes, and soon the 
cell-contents of these are seen to have arranged themselves 
in spiral lines corresponding to this movement. Some of 
these retain their straight condition, while others become 
bent around so as to form almost a complete circle, and then 
proceed onwards by a rolling motion. There is a regular 
and determined passage from one of these states to the other, 
as I was able to ascertain by careful watching ; but the most 
