LESSON 79.] NERVOUS SYSTEM IN LAMELLIBBANCHIATA. 259 



of their prehensile organs the animalcules adapted for their suste- 

 nance." The microscopical examination of the contents of the sto- 



FIG. 877. 



Nervous system, Terebratula Australis. 

 a. Ganglion. 5, 5. Nerves of the mantle, c, c. Veins, d. Nerves of the arms. 



machs of numerous Terebratulae, has uniformly disclosed to view 

 myriads of well known minute siliceous forms erroneously ascribed 

 by Ehrenberg to the animal kingdom. 



LESSON LXXIX. 



NEEVOUS SYSTEM IN THE LAMELLIBEANCHIATA (LAMELLA, A PLATE; 

 BRAG CHI A, GILLS); 



1177. The relation of the contained soft parts to the bivalve shell 

 of the Brachiopoda is such that, in the Terebratula^ the perforated 

 valve must be regarded as the inferior or central one, and the imper- 

 forate or shorter valve the dorsal one. 



1178. In the Lamellibranchiata one valve is applied to the right 

 and the other to the left side of the animal. 



1179. The nervous system advances in a regularly proportional 

 degree with the complexity of the general organization, and especially 



