n6 MORPHOLOGICAL TYPES 



Characters of Lacerta > lacking in lower forms , and common to 

 Amniota : 



Embryos develop on land within an Amnion and a 

 shell ; 



Metanephros and ureter ; 



Spinal accessory and Hypoglossal nerves emerge from 

 the skull ; 



Superficial grey matter (cortex) in the cerebral hemi- 

 spheres ; 



Breathing effected with the help of the ribs ; 



Jacobson's organ ; 



Development of saccule, tympanic cavity (spiracular 

 pouch), and conversion of the hyomandibula into the 

 columella auria. (Already present in the frog, though 

 feebly developed in Triton) ; 



Atlas and Axis vertebrae differentiated ; 



Copulatory organs developed ; 



Ischio-pubic foramen present. 



Characters of Lacerta which are typical of Reptiles : 



Skin covered with horny scales ; 



Ventricle of the heart incompletely divided (except in 

 Crocodiles). 



Literature. 



Parker, T. J. A Course of Instruction in Zootomy (Vertebrates). 

 Macmillan, London, 1884. 



