THE SLOW-WOKM, AN GUIS FRAGILIS 27 



lizards) ; while in the snakes a single large broad scale 

 extends from one side of the belly to the other. 

 Thirdly, the tail in the slow -worm is as long as the 

 body ; in the snakes it is shorter than the body. On 

 dissection, other differences would become apparent, 

 and it may be convenient here to sum these dis- 

 tinctions up in tabular form for reference. 



Lacertilia or Lizards. 



Limbs present or rudiments. 

 Eyelids present. 

 Belly scales in several rows. 

 Jaws firmly united. 

 Teeth conical (as a rule). 

 Tongue notched. 

 All are innocuous. 

 Sternum present. 

 Urinary bladder present. 



Ophidia or Snakes. 



Limbs absent. 



Eyelids absent. 



Belly scales in one row. 



Jaws widely distensible. 



Teeth recurved. 



Tongue deeply bifid. 



One British species venomous. 



Sternum absent. 



Urinary bladder absent. 



It is the rudimentary limbs that have caused the 

 blind-w^orm to be regarded as a snake by the ignorant. 

 No sign of these appears externally, but a careful 

 dissection reveals the x^i'^sence of the rudimentary 

 pelvic girdle which, in the limbed forms, articulates 

 with the hind limbs. This lizard is from this point 

 of view, therefore, intermediate between the snakes 

 and lizards with limbs, — one of the many connecting 

 links found in nature indicating the gradual evolu- 

 tion of creatures from generalised to specialised 

 types. 



Distribution. — The slow-worm, or blind-worm, is 



