INTRODUCTION 



ancestors akin to sea-squirts, and man may have done so too, 

 though less dramatically, from ancestors akin to apes; for the 

 fundamental pattern of a vertebrate is indeed that of the larva 

 of a sea-squirt, upon which the feeding mechanism of the adult 

 has somehow been superimposed; and the story of how man 

 may have taken origin from a foetal ape became science fiction 

 not so long after it made claim to being science fact. But I feel 

 obliged to report that speculation on paedomorphosis is tend- 

 ing to get a little out of hand. In the old days, if animal A had 

 a B-Vike stage in its life history, that was taken as certain 

 evidence that A had evolved from B and that its transiently 

 B-Yike condition was an example of HaeckePs '"Law of Re- 

 capitulation'', viz. that an animal, as it develops, climbs up its 

 own family tree. To-day no one believes in recapitulation in 

 this simple form, and when A has a j5-like stage in its life 

 history, it tempts people to declare that B arose bv paedo- 

 morphosis from an ancestor akin to A. All the evidence that 

 was at one time thought to exemplify recapitulation is now 

 inverted and used as e\'idence of a paedomorphic origin: 

 Haeckel is still the hero, though his portrait hangs upside 

 down: but neither way up can Haeckel wield his old authority 

 without better evidence than his successors have so far been 

 able to provide. 



Nothing in evolutionary thought shows up the difference 

 between professional and layman so clearly as their attitude 

 towards Lamarckism, the subject of the fourth of the essavs 

 printed here. Nearly all laymen, and most young zoologists 

 before they learn better, believe implicitly in what has come to 

 be called, no matter how inappropriately, the ''inheritance of 

 acquired characters\ It is an intelligible and forthright doc- 

 trine, and, in ignorance of genetics, an alternative is difficult 

 to propound; more than that, a certain deep-seated sense of the 

 fitness of things is gratified by the belief than an animaPs own 

 activities, accomplishments and endeavours should contribute 



13 



