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 amuch more superficial character than might have been 
suspected, and that reptiles and birds do really agree much more 
closely than birds with mammals, or reptiles with amphibians. But 
still, “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, 
