Chapter Fifteen 



CHORDATA 



The Chordata is the highest phylum of the ani- 

 mal kingdom. It is in this group that all the higher 

 animals are found, even including man. The main 

 characteristic of the phylum is the possession— some- 

 time during life — of a notochord. In higher chor- 

 dates this notochord becomes surrounded with car- 

 tilage or bone and becomes the spinal column. The 

 higher groups of chordates — those that possess a 

 backbone — are the vertebrates and include the fishes, 

 amphibia, reptiles, birds and mammals. 



There are a few groups of chordates that do not 

 possess a backbone and therefore are invertebrates 

 and are to be considered in this book. In many of 

 these lower chordates the notochord remains 

 throughout life; in others it disappears after a larval 

 stage. 



ENTEROPNEUSTA 



Worm-like chordates in which the notochord 

 consist of a hollow dorsal projection of the forward 

 part of the digestive tube. 



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