306 The Field Naturalist' s Quarterly November 



between the ordinary four-limbed type and the absolutely 

 limbless species of which the slow-worm is an example. 



It has been said that a burrowing habit, or a life amidst 

 sand, might be regarded as conditions under which limbs 

 would be not altogether an advantage, and, as a matter of 

 fact, it will be found that it is precisely in those lizards 

 which live under these conditions nowadays that this partial 

 or complete absence of limbs is to be observed. It is, too, 

 almost certain that the laws of the past in biology have been 

 very similar in their methods of operation to those of the 

 present. 



Along with this reduction in the size of the limbs in 

 lizards is found an elongated trunk or body, approaching 

 the shape of that of a serpent. This is seen, for example, 

 in the slow-worm. This long body may be associated with 

 a shortened tail or not ; in the slow-worm the tail is as long 

 as the body. In many-limbed lizards the tail is, of course, 

 considerably longer than the body, as in the viviparous 

 lizard. Then we find that in the limbless lizards there are 

 some vestiges of the limbs or limb girdles usually found 

 under the skin. Those of the hind-limbs lie immediately 

 in front of the anal aperture. A very interesting point 

 is that the fore-limbs disappear before the hind-limbs, or 

 are frequently smaller than the hind-limbs. Some species 

 have hind-limbs only, while rarely the opposite condition 

 occurs, e.g. in Ckirotes canaliculatus, a species found in 

 Mexico and California, in which there are still fore-limbs 

 with four clawed digits. This family (Amphisbaenidae) 

 includes a number of species which are burrowing in 

 habit and limbless ; Ckirotes being the only species with 

 limbs. In most cases the pectoral and pelvic girdles are 

 to be found in a vestigial condition ; but in one family 

 (Dibamidae) not merely the limbs, but the limb girdles 

 also are absent, though in the males there are flaps which 

 seem to indicate limbs. The family to which the slow- 

 worm belongs (Anguidae) seem to be in a state of change, 

 there being a general tendency to reduce and lose the 

 limbs, which " may be more or less developed, or entirely 

 absent externally, in which case, however, the rudiments of 

 the pectoral and pelvic arches are always present" {British 



