76 NOTES AND MEMORANDA. 



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 vio- 

 lent 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 

 vigorous and at the same time the cilia disappeared one by 

 one, melting out of view, being apparently absorbed again 

 into the mass from which they were originally developed. 

 At the same time one of them seems to elongate initil 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, Avhile 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 subsides, while 

 the clear end becomes more pointed, and now tbe ci'eature 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 resembling very closely that seen to 

 take place in the intestines of animals, and known as peri- 

 stalsis, takes place. Many individuals move directly and 

 straight onwards, preserving their body perfectly rigid, so 

 tbat after a time the cell-contents are seen to arrange them- 

 selves 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 com- 

 plete 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 remarkable fact connected with the 



