THE WONDER OF LIFE 485 



revived after five years. One of these was a small Flagel- 

 late, Oikomonas termo. 



Local Life. — The phenomena of local hfe demand care- 

 ful consideration. On the one hand, we have many cases 

 of fragments which grow into wholes. On the other hand, 

 we have curious examples of parts which can hve on for a 

 long time after the whole has been destroyed, though they 

 show httle or no power of regeneration. Let us illustrate 

 the first set of cases first. Every one knows that a piece 

 of a branch or a piece of a potato will remain ahve for a con- 

 siderable time after being cut off, and will in appropriate 

 conditions grow into a complete plant. Posts of wood, 

 beheved to-be dead, sometimes burst into leaf after they have 

 been driven into the ground. A small fragment of many a 

 plant, from Liverwort to Begonia, will grow into a complete 

 plant. And similarly, a fragment of sponge, of hydroid, of 

 sea-anemone, of certain worms, and so forth, can regrow the 

 whole. There is need of precise experiment to determine 

 the limits and conditions of these regenerations of wholes 

 from parts. In the case of Hydra, it has been foimd that 

 the regenerating fragment must not be too small — a quanti- 

 tative limit, and that it must contain samples of the 

 different kinds of cells in the body — a quahtative hmit. 

 A tentacle will not regrow a polyp, though a polyp soon 

 regrows a tentacle. Very extraordinary are the recent 

 experiments of Professor H. V. Wilson which show that 

 some sponges may be minced up and strained through a 

 cloth strainer — and yet the debris poured out in an appro- 

 priate place will develop into a proper sponge. It is a 

 verification of one of the old myths — of Zagreon, who 

 was cut into pieces and yet survived. 



As to the second set of cases, where parts hve on though 



