144 UNIVERSALITY OF DEGENERATIVE EVOLUTION 



2. The Frog. The vertebral column in the 

 frog consists of nine vertebrae and the coccyx 

 (urostyle). 



The first vertebra (the proatlas), which is fully 

 functional, retains a centrum and two well-developed 

 neurapophyses, but the transverse processes, the 

 intercentrum, the haemapophyses and the ribs have 

 all disappeared. 



The eight following vertebrae each have a 

 centrum, neurapophyses and transverse processes 

 which at least partially represent the ribs. 



The coccyx, whether it be formed by the 

 lengthening out of the last caudal vertebra or by 

 the fusion of several, is undoubtedly part of the 

 vertebral column which has been transformed. 

 The coccyx of the frog is equal in length to the 

 whole of the remaining part of the vertebral 

 column, and is fully functional ; it serves as a 

 support to the pelvic region and fulfils the part of 

 a sacrum from the physiological point of view. 

 The coccyx, excepting at its commencement, con- 

 sists of only one centrum, or of several fused 

 centra, all other elements of the vertebrae have 

 disappeared. Here then is an animal in which the 

 modifications of the vertebral column have been 

 attended by the following retrogressive phenomena : 

 in the upper part of the vertebral column from 

 three to five parts of the vertebrae have disappeared ; 

 in the lower half, all the parts, excepting one, are 

 gone. 



