19 
transformation. The full-grown Frogs and Toads are of all 
Vertebrates the most absolutely taillest. Hence they are called 
Anura; that is, ‘‘ without tails.” 
There is a remarkable fact about these temporary tails. The 
notochord in them remains, without-any ossification, as if it were 
not worth while to grow them; whereas in the permanently tailed 
amphibians, such as the efts, the bony spine extends along the 
tail. 
In Reptiles the tail is very often massive, and clearly a continuation 
of the trunk ; still being used as a swimming or wriggling organ. 
Some kinds of lizards, when seized by the tail, throw it off; or 
rather, it is broken off by violent muscular action. Our common 
Lizard, and also the Slow-worm, have this habit. I+ has been 
thought to be useful to the animal; inasmuch as the violent 
wriggling of the loose tail may attract attention, while the body 
runs away. 
Some lizards, as the one called Basilisk, have a crest on the 
back and on the tail. The tendency to the formation of this may 
possibly be inherited from their amphibian or fish-like ancestors, 
which had a dorsal fin. 
A prehensile or grasping tail is found in the Chameleon tribe, 
and in many snakes. The Slow-worm has a tendency that way. 
On the other hand, the Tortoises have comparatively short tails. 
Perhaps the most singular modification in Reptiles is the rattle 
of the rattle-snakes. This consists of several loose rings of skin, 
and is sounded by shaking the end of the tail. There is a 
rudiment of it in some other snakes. 
One kind, that has no rattle, was observed by Darwin, shaking its 
tail like a true rattle-snake, so as to make a noise by striking 
against the grass, &c. This gives us some clue as to the way in 
which the rattle may have originated. As to its use, it has been 
suggested that the sound may serve to warn predacious animals of 
the dangerous nature of their intended victim, and so save it from 
attack. 
From the Reptiles let us pass to their modified relatives, the 
Birds. Although the modern bird’s tail is the greatest possible 
contrast to the long sealy one of the lizard, yet one of the 
“‘missing links” is still to be seen in the fossil Archeopeteryx. 
This extinct creature had a long, tapering, jointed tail, like a 
lizard; but each vertebre bore a pair of large quill-feathers 
‘Spreading horizontally. These feathers on the tail, with those on 
the wings, were very likely the only ones it possessed. See Fiy. 9. 
In the birds of the present day the caudal vertebre are few, and 
very short ; the last are joine 1 together into the so-called « plough- 
share bone,” which supports tlie whole set of quill feathers. The 
