CREATION BY EVOLUTION 



very perfectly preserved fossil specimens of Cephalaspis from 

 the Devonian rocks of Spitzbergen. Serial sections of these 

 specimens have been studied by Professor Patten, who states 

 that the radiating bony channels for the cranial nerves and 

 many other architectural features of the anatomy of the head 

 conform to the general plan seen in the head of the fossil 

 eurypterids and other arthropods. Patten therefore argues 

 that this new material has proved his theory that the verte- 

 brates have been derived from the arthropod stock. 



Whether the vertebrates came from very early arthropods 

 or whether they were derived from unknown cigar-shaped 

 forms that preceded both the ostracoderms and the existing 

 lancelets (Amphwxus), it is at least certain that the earliest 

 known ostracoderms already foreshadowed the higher verte- 

 brates, including man, in the ground plan of their organiza- 

 tion. Already they had the main chordate characters that 

 are displayed in the human embryonic and foetal stages but 

 that are masked in the adult human stage, namely, a noto- 

 chord or elastic axis, above which is the central nervous sys- 

 tem and below which is the primitive gut and heart. 



Like all primitive chordates the ostracoderms swam head 

 on, by throwing the long body into waves proceeding from in 

 front backward. This undulating motion is produced by the 

 rhythmic contractions of a series of zigzagging muscle plates 

 ranged along each side of the body from behind the head 

 to the base of the tail. Each zigzag is separated from the 

 next by a partition of connective tissue which runs inward 

 toward the notochord. 



The ultimate unit of locomotion is not the zigzag muscle 

 segment but the short red muscle fibre. Thousands of these 

 little fibres are placed along the zigzag path of the muscle 

 segment, each fibre being attached at its front and rear ends 

 to the connective tissue partitions between die segments. 



[274] 



