126 ANTHROPOID APES. 



phosis, and, after their modification into sacral verte- 

 brae, have assumed their fourth form as coccygeal 

 vertebrae. 



Froriep, a follower of Eosenberg, remarks that the 

 lumbo-sacral vertebrae, i.e. those constituents of the 

 vertebral column which form the transition from 

 the lumbar to the sacral vertebrae, are invested with 

 fresh interest by Rosenberg's hypothesis. Accord- 

 ing to their position in the vertebral column, they 

 are to be regarded as lumbar vertebrae, introduced 

 too early or too late into the structure of the sacrum. 

 If the twenty-fourth vertebra is assimilated with the 

 sacrum, so as to form an upper promontory or out- 

 work, this variety offers a point of transition to a 

 future formation (?) in which this vertebra normally 

 becomes the first sacral vertebra, and the column will 

 now display tweuty-tliree free vertebrae. If, again, 

 this transition occurs in the twenty-fifth vertebra of 

 the series, which thus becomes the chief sacral verte- 

 bra, this is, in Eosenberg's opinion, a characteristic 

 survival of the racial development, an atavism.* 



According to Welcker's theory, the chief sacral 

 vertebra in one animal corresponds to the same 

 sacral vertebra in another animal, whatever their 

 number may be. The cervical vertebrae of one 

 animal, which may be five, seven, or even eleven in 

 number, correspond to the cervical vertebrae of 

 another animal. The vertebral column of one 

 animal corresponds to the vertebral column of 

 another, taken as a whole, but not to two- thirds or 

 three-fourths of that column. In accordance with 



* Beitrdge zur Gehurtsliulfe, p. 161. 



