68 Royal Institution : — 



I believe that these excuses have very great force ; but I cannot 

 smother the uncomfortable feeling that they are excuses. 



If a landed proprietor is asked to produce the title-deeds of his 

 estate, and is obliged to reply that some of them were destroyed in a 

 fire a century ago, that some were carried off by a dishonest attorney, 

 and that the rest are in a safe somewhere, but that he really cannot 

 lay his hands upon them, he cannot, I think, feel pleasantly secure, 

 though all his allegations may be correct and his ownership indis- 

 putable. But a doctrine is a scientific estate, and the holder must 

 always be able to produce his title-deeds, in the way of direct evi- 

 dence, or take the penalty of that peculiar discomfort to which I have 

 referred. 



You will not be surprised, therefore, if I take this opportunity of 

 pointing out that the objection to the doctrine of evolution, drawn 

 from the supposed absence of intermediate forms in the fossil state, 

 certainly does not hold good in all cases. In short, if I cannot pro- 

 duce the complete title-deeds of the doctrine of animal evolution, I 

 am able to show a considerable piece of parchment evidently belong- 

 ing to them. 



To superficial observation no two groups of beings can appear to 

 be more entirely dissimilar than reptiles and birds. Placed side by 

 side, a Humming-bird and a Tortoise, an Ostrich and a Crocodile 

 offer the strongest contrast, and a Stork seems to have little but ani- 

 mality in common with the Snake it swallows. 



Careful investigation has shown, indeed, that these obvious differ- 

 ences are of a much more superficial character than might have been 

 suspected, and that reptiles and birds do reaUy agree much more 

 closely than birds with mammals, or reptiles with amphibians. But 

 stiU, " though not as wide as a church-door or as deep as a well," 

 the gap between the two groups, in the present world, is considerable 

 enough. 



Without attempting to plunge you into the depths of anatomy, 

 and confining myself to that osseous system to which those who desire 

 to compare extinct with living animals are almost entirely restricted, 

 I may mention the following as the most important differences be- 

 tween all the birds and reptiles which at present exist. 



1. The pinion of a bird, which answers to the hand of a man or 

 to the fore paw of a reptile, contains neither more nor fewer than 

 three fingers. These answer to the thumb and the two succeeding 

 fingers in man, and have their metacarpals connected together by firm 

 bony union, or ankylosed. Claws are developed upon the ends of at 

 most two of the three fingers (that answering to the thumb and the 

 next), and are sometimes entirely absent. 



No reptile with well-developed fore limbs has so few as three fin- 

 gers ; nor are the metacarpal bones of these ever united together ; 

 nor do they present fewer than three claws at their terminations. 



2. The breast-bone of a bird becomes converted into a membrane 

 bone, and ossification commences in it from at least two centres. 

 The breast-bone of no reptile becomes converted into a membrane 

 bone, nor does it ever ossify from several distinct centres. 



