220 CHORDATA 



Nemertean Theory. — The Nemerteans, probably related to the 

 Platyhelminths, were suggested as having affinities with vertebrates, 

 by Hubrecht. His theory attempts to homologize the proboscis 

 sheath of the Nemertean with the notochord of the chordate. He 

 suggests that the vertebrate nervous system developed from the 

 three nerve cords of a Nemertean. The dorsal nerve cord of the 

 Nemertean became the central nerve system and the lateral nerve 

 cords persist in the rami lateralis X, of the lower vertebrates. As 

 the other organs of the animals are not similar in arrangement the 

 theory seems of little importance. 



References on the Origin of Vertebrates 



Delsman, H. C. 1922. The Ancestry of Vertebrates as a Means of 

 Understanding the Principal Features of Their Structure and 

 Development. Weltevreden (Java). 



Gaskell, W. H. 1908. The Origin of the Vertebrates. London, 

 Longmans-Green. 



Hubrecht, A. A. W. 1883. On the ancestral form of the Chordata. 

 Quart. Jour. Micr. Sci., N.S., 23: 349-368. 



Lull, R. S. 191 7. Organic Evolution. New York, Macmillan. 



MacBride, E. W. 1914. Text-book of Embryology. Vol. i, Inverte- 

 brate. London, Macmillan. 



Newman, H. H. Vertebrate Zoology. New York, Macmillan. 



OsBORN, H. F. 1917. The Origin and Evolution of Life. New York, 

 Scribners. 



Patten, W. 191 2. The Evolution of the Vertebrates and their Kin. 

 Phila., Blakiston. 



Patten, W. 1920. The Grand Strategy of Evolution. Boston, R. G. 

 Badger. 



Wilder, H. H. 1909. History of the Human Body. New York, Holt. 



