140 THR AUSTRALIAN NATURALIST. 
trees, and have special structures developed for this work. 
These are adhesive lamellae arranged on the under-surface of 
the digits. Feratoscincus, a gecko living in this desert region, 
where it runs about on the sand, has digits without these 
lamellae, but they are granular below and_ strongly-fringed 
laterally to enable it to run quickly on the sand. Instead of 
the soft granular skin on its upper surface, such as one gen- 
erally finds in geckos, its back and upper parts are protected by 
a hard, scaly covering. The uppereyelids are enlarged so as to 
keep the sand out of its eyes. 
Phrynocephalus, one of the Agamidae, a family of lizards of 
which our common jew-lizard is a typical member, lives in 
this desert, and has long lateral fringes on its digits so as to 
enable it to run quickly on the sand. Its body is flattened or 
depressed in form, and devoid of dorsal crest, and there are 
lateral folds of skin on the body, by means of which it can 
shake sand over itself and rapidly disappear from view. It 
runs so fast that one can scarcely see anything but its shadow. 
Tt can change its direction of motion like lightning, and with 
a pause in its flight, by a few dexterous shakes of its lateral 
folds, it is covered with sand and has disappeared from view. 
To protect its special sense organs from the sand there is no 
external ear opening at all, and the margins of its eyelids are 
broadened into plates, which keep the sand ont of its eyes. 
A very interesting feature in lizards is the power they have 
of regenerating lost parts. Many lizards, having lost the tail, 
can grow a new one, but this phenomenon is perhaps best seen 
in thegeckos. The fat, swollen-looking tails of these interesting 
little creatures can be thrown off at will. When pursued by 
an enemy and almost in its clutches, the tail is. thrown off ; 
and while the aggressor delays to devour the tail the gecko 
makes good its escape. The break always occurs in the middle 
_ of a vertebra, where there is a plate of cartilage, the cells of 
which have retained their youthful character, and from this 
plate mainly the new tail is produced. But instead of a spinal 
column, only a cartilaginous rod is produced, so that the new 
tail is in reality only an imitation one. It is an interesting 
point that this is a reversion to a very primitive type, for in 
the very lowest of the vertebrates the whole spinal column 
exists in this form, The arrangement of the scales on the new 
tail, too, is often different from that of the original tail, and 
resembles that of an ancient ancestral form of the lizard in 
question. 
The pineal body or pineal eye is a well-marked structure in 
lizards. tis a process found in’ all craniata, given off from 
the dorsal surface cf the brain. It consists of a proximal 
narrower part known as the stalk, and a more rounded terminal 
part the pineal body. It lies quite close to the surface of the 
