THE LIFE CYCLE 279 



gen, and breathing out of carbonic-acid gas, movement, 

 feeling, etc. But some animals can actually suspend all 

 of these functions, or at least reduce them to such a mini- 

 mum that they can not be perceived by the strictest exami- 

 nation, and yet not be dead. That is, they can renew 

 again the performance of the life processes. Bears and 

 some other animals, among them many insects, spend the 

 winter in a state of death-like sleep. Perhaps it is but sleep ; 

 and yet hibernating insects can be frozen solid and remain 

 frozen for weeks and months, and still retain the power of 

 actively living again in the following spring. Even more 

 remarkable is the case of certain minute animals called Ro- 

 toftoria and of others called Tardigrada, or bear-animalcules. 

 These bear-animalcules live in water. If the water dries 

 up, the animalcules dry up too ; they shrivel up into form- 

 less little masses and become desiccated. They are thus 

 simply dried- up bits of organic matter; they are organic 

 dust. Now, if after a long time years even one of these 

 organic dust particles, one of these dried-up bear-animal- 

 cules is put into water, a strange thing happens. The body 

 swells and stretches out, the skin becomes smooth instead 

 of all wrinkled and folded, and the legs appear in normal 

 shape. The body is again as it was years before, and after 

 a quarter of an hour to several hours (depending on the 

 length of time the animal has lain dormant and dried) slow 

 movements of the body parts begin, and soon the animal- 

 cule crawls about, begins again its life where it had been 

 interrupted. Various other small animals, such as vinegar 

 eels and certain Protozoa, show similar powers. Certainly 

 here is an interesting problem in life and death. 



When death comes to one of the animals with which 

 we are familiar, we are accustomed to think of its coming 

 to the whole body at some exact moment of time. As we 

 stand beside a pet which has been fatally injured* we wait 

 until suddenly we say, " It is dead." As a matter of fact, 

 it is difficult to say when death occurs. Long after the 



