ANIMAL KINGDOM. 231 



or tentacula, situated at the lower extremity of the above- 

 mentioned cavity. The internal coats of this branchial 

 cavity are covered over with a reticulation of minute veins, 

 which cross one another at right angles. Those which 

 are vertical come from the transverse veins, which again 

 are connected by their extremities with two large vertical 

 trunks, each occupying one of the sides of the whole ca- 

 vity. These two vessels open at opposite ends into the 

 heart, which is of nearly the same diameter with them, 

 and merely distinguished by being fusiform and more mus- 

 cular. JVl . Cuvier conceives one of these trunks, which 

 opens into the heart, to be the branchial vein by which 

 the blood passes into the heart, and the other, which is 

 much the longest, to be the Aorta distributing the blood 

 throughout the body. So that the Ascidia have a system 

 of circulation corresponding to that of the Gasteropoda and 

 Acephalous Mollusca, that is, they have only the left or 

 Aortic Ventricle without any other at the reunion of the 

 Perm cava and pulmonary Artery. The Ascidice have a 

 liver like that of the Acephalous Mollusca. It is of a 

 darkish colour, and adheres in an intimate manner to the 

 sides of the stomach, into which the bile is distributed by 

 several orifices which are for that purpose in its sides. 

 The nervous system consists, so far as has yet been obr- 

 served, of but one ganglion, which is situated in the sub- 

 stance of the tunic and between the branchial and anal 

 apertures. Amongst the numerous ramifications of medul- 

 lary matter which proceed from this ganglion are two or 

 three which go towards the oesophagus and there sur- 

 round it with a nervous ring, which Cuvier considers to be 

 the brain. This nervous system corresponds with that o-f 

 tJae bivalve or Acephalous Mollusca. On the whole then, 



