THE WONDER OF LIFE 595 



(C) Habituation. What is true of the results of environ- 

 mental influence holds good in regard to function. A 

 sequence of activities often performed leads to the estab- 

 lishment of a habit, which is associated with a structural 

 change in the nervous system. As we say, paths are 

 established along which nervous messages pass swiftly 

 and smoothly. Experiments, such as some of those alluded 

 to in the chapter on "The Ways of Life," show clearly that 

 the individual organism can in various degrees become 

 habituated, and it is plainly advantageous to it to have 

 engrained reactions, tropisms, rhythms and instincts. 

 Eeady-made effective answers to frequently recurring 

 questions save time and energy, and often the life of the 

 creature. In many cases there is no time for experiment- 

 ing or deliberating, the answer must be instantaneous if 

 it is to be any good at all. But this brings us to the difficult 

 fact that it is often with more than individual habituation 

 that the organism gives its ready-made answer such as 

 passing into hibernation on the approach of winter, or 

 flying south in the autumn. Antecedent to its individual 

 experience, it exhibits the effective reaction. 



(D) Transmissibility of Acquired Characters. 

 In the case of a Protozoon, such as an Amoeba or a Slipper 

 Animalcule, the problem is simple. The unicellular creature 

 gathers experience ; its organization is definitely affected ; 

 it has learned a lesson. This is not for itself alone but for 

 its race, for it multiplies by dividing into two, and each 

 of the daughter-cells shares in the organization which has, 

 so to speak, learned a lesson. Each new unit can then go 

 on to learn the lesson a little better, and so we have the 

 rudiments of behaviour in these relatively simple living 

 creatures. There^is no doubt here that the race profits 



