THE FACT OF RECAPITULATION. 63 



type. In its earliest stage, every organism has a great 

 number of characters in common with other organisms in 

 their earliest stages ; at each successive stage the series of 

 embryos which it resembles is narrowed. The rabbit begins 

 like a Protozoon as a single cell, after a while it may be com 

 pared to the young stage of a very simple vertebrate, after 

 wards 'to the young stage of a reptile, afterwards to the 

 young stage of almost any mammal, afterwards to the young 

 stage of almost any rodent, eventually it becomes unmistake 

 ably a young rabbit. 



Herbert Spencer expressed the same idea, by saying that 

 the progress of development was from homogeneous to 

 heterogeneous, through steps in which the individual history 

 was parallel to that of the race. But Haeckel has illustrated 

 the idea more vividly, and summed it up more tersely than 

 any other naturalist. His " fundamental biogenetic law " 

 reads, " Ontogeny, or the development of the individual, is a 

 shortened recapitulation of phylogeny, or the evolution of 

 the race." 



It is hardly necessary to say that the young mammal is 

 never like a worm,' or a fish, or a reptile. It is at most like 

 the young stages of these. 



Moreover, the individual life-history is much shortened 

 compared with that of the race. I do not mean merely that 

 the one takes place in days, while the other has progressed 

 through ages, but stages are often skipped, and short cuts 

 are discovered. And again, many young animals, especi- 

 ally those " larvse " which are very unlike their parents, 

 often exhibit characters which are secondary adaptations to 

 modes of life of which their ancestors had probably no experi- 

 ence. In short, the individual's recapitulation of racial 

 history is a general, but not a precise, statement of the facts. 



Finally, we do not clearly understand how the recapitu- 

 lation is sustained. Has the embryo a feeling for history, 

 or some unconscious memory of the past ? Recapitulation is 

 due to no dead hand of the past, but to physiological condi- 

 tions which we are unable to discover or express. The fact 

 of reca])itulation has been recently discussed with great care 

 by Prof. Milnes Marshall,^ — in his Presidential Address to 

 the Biological Section of the British Association, 1890, — 

 published in Nature, September of that year. 



