124 



THE EVOLUTION OF THE METAZOA 



Fig. 22. Scyphozoa, Lucernariidae. K,'Lticernaria sp. (from Hyman). 

 B, Halidystus auricula (after H.J. Clark). 



scyphopolyp and of a distal scyphomedusa. The same combi- 

 nation can also be found in its muscle system ; in one and the 

 same individual we can find the peculiarities of a polyp as well 

 as those of a medusa, i.e. on one hand, the taeniolan or septal 

 muscles, and the coronal muscles in the form of bands, as 

 well as the radially oriented muscular tissue of the oral disc 

 (manubrium). 



The Nervous System 



Cnidaria have played a special role in the history of the 

 development of neurology. Nobody has succeeded so far in 

 finding either individual nerve cells or, even less so, a real 

 nerve system in Spongiae; this is the true situation in spite of 

 the contrary assertions made by Tuzet and by her collaborators. 

 On the other hand it has been possible to identify in Cnidaria, 

 and especially in Hydra which has been intensively studied, not 



