Later on the foetus takes a mammalian form, ■vrith a highly 

 respectable tail, and later still the purely human characters. 

 What is true of the general form is also true of particular 

 organs. The heart, for example, is at first a simple mus- 

 cular tube, and then takes on fishlike, and later, reptilian 

 characters, before it becomes completely mammalian in 

 structure. At an early period of development man has gill- 

 slits like a fish, and occasionally an unfortunate child is 

 bom with an unclosed gill-slit. What is true of man is 

 true of the entire organic world. All the higher animals 

 and plants pass through the same changes in their develop- 

 ment as are represented by the permanent aduit conditions 

 of lower forms, still living or extinct. Characters unessen- 

 tial to subsequent development, but formerly of importance 

 to ancestral forms, tend to appear earlier in development, 

 to become shortened in their operation, and eventually to 

 disappear. But salient points of the development of 

 the species are always more or less represented in the 

 development of the individual. 



A striking example of the correspondence of certain 

 stages of individual development with previous adult forms 

 is supplied by the stag. Macaulay's schoolboy knows that 

 the stag has only one point to his antlers the first year ; 

 the next year he has two points, the next three, so that you 

 can tell the age of a stag by the number of his points. 

 Now, in the middle miocene the fossil stag is found with 

 two-pointed antlers, in the upper miocene with three points, 

 'acquiring more in the lapse of geological time, until we 

 find him full antlered in the upper pliocene. 



Let us now take the evidence afforded by rudimentary 

 structures. And if any one is disposed to regard with sus- 

 picion the evidence of the comparative morphology of 

 creatures other than man in its bearing on man, I will 

 appeal from Ceesar unto Ceesar : I will discuss the point 

 from the structure of man himself. I have already had 

 occasion to mention that we have all of us rejoiced, happily 

 before birth, in a conspicuous caudal appendage. And 

 any one acquainted with the human skeleton will not fail 

 to recognise in the coccygeal bones a very palpable rudi- 

 mentary tail — a dwarfed and unnecessary member. 



In the external ear of man we have remarkable evidence 

 of dwindled rudimentary organs, representing structures 

 of the highest functional value in allied mammalia. Not 

 merely does the apex possess a fold, the secret of which is 



