LIFE'S SIMPLEST CHILDREN. 17 
animals higher in the world than itself; and lastly, it 
grows and increases, for when it is too large to be 
comfortable it splits in two, and each half goes its 
way as a living animal. 
Let us see how one behaved which Professor 
Haeckel took out of the sea and kept in a watch- 
glass under a microscope. When he first looked at 
it he found that it was drawn up in a lump with a 
minute animal and a plant-cell in the middle of its 
slime, and close by it in the water lay a small living 
animal called a Ceratium (c, Fig. i), which has a 
hard case or shell. After a while, as he watched, 
he saw the thread-slime put out its fine threads on 
all sides (a, Fig. i). Soon the threads on the right 
side touched the shell of the Ceratium. Here was 
food, and the body of the Thread-slime evidently 
became aware of it at once, for all the little grains in 
the slime began to course to and fro, and the threads 
touching the Ceratium lengthened out and stretched 
more and more over it, while all those on the other 
side which had not found any food were drawn in. 
(b, Fig. i). Six hours later when Dr. Haeckel looked 
again, to his astonishment the thread -slime had 
disappeared, but on examining more closely he 
discovered it completely spread in patches over the 
shell of the Ceratium. It had drawn its whole body 
after the pioneering threads and wrapped itself round 
its prey. Next morning when he looked again, lo ! 
it was back in its original place, and by its side lay 
the Ceratium shell quite empty, together with the 
skeletons of the other two forms which had been 
inside the Thread-slime ! 
This little drop of slime without eyes or ears or 
