THE WONDER OF LIFE 591 



develop in the shelter of the inner gill-plate within little 

 sacs, and the point is that these are in the main due to the 

 activity of leucocytes. In other words, they arise by a 

 process analogous to inflammation. After the embryos 

 are liberated the gill-plate requires considerable patching 

 up, especially as regards its epithelial covering. 



TRADING WITH TIME 



In a preceding chapter we gave illustrations of life's 

 victory over difficulties. The most uninviting corners of 

 the earth and sea are explored and exploited ; the most 

 unpromising habitats become comfortable homes ; a 

 table is spread in the wilderness ; there is sometimes, as 

 we have seen, an amazingly successful recklessness, and 

 in cases like the migratory birds who literally ' know no 

 winter in their year ', we are face to face with an achieve- 

 ment which seems not far short of getting the better of 

 Time. 



(A) Registering Experience. The beginning of the 

 organism's business of trading with time was not far from 

 the beginning of living organisms themselves. We are not 

 sure that a living creature was worthy of the name until 

 it became able to register its experience, until it was 

 able to profit by what happened to it. They say that the 

 bar of iron once struck remembers the blow, which seems 

 to us rather an abuse of metaphor, but, as we believe in 

 the value of metaphor as a scientific instrument, we do 

 not press our objection. We would ask, however, whether 

 the smitten bar of iron, or the jarred crystal, or the jewel 

 whose sanctity was violated, remembers the experience 

 to its own advantage, for that is what the organism does. 

 Its premiums paid to experience are its own best treasures. 



