ANIMAL KINGDOM. 317 



principal argument however is, that since these animals 

 are always found collected in numbers together, this in- 

 clination to assemble cannot result from hazard but from 

 sexual instinct ; but were this mode of reasoning correct, 

 Oysters and Ascidia would not be hermaphrodites. By 

 galvanic experiments he convinced himself of the dispo- 

 sition of the nervous matter, and found it to correspond 

 with the form of the animal. At the lower surface of the 

 body, near the reunion of the two hepatic vessels of each 

 ray, are found for each of these two grayish ganglions re- 

 sembling an elongated grain of millet, and communicating 

 together by a transverse filament. From each double 

 ganglion proceed filaments to the mouth and stomach, but 

 the principal and longest branch which leaves each gan- 

 glion is that which ramifies into each ray. This radiated 

 nervous system, so different from all the others which we 

 have examined, may be considered as the type to which 

 the nervous structure of all the Radiata may be referred. 



ZOANTHIDA. 



The Zoanthus sociatus of Cuvier, or Hydra sociata of 

 Gmelin, has the same fleshy tissue, the same disposition 

 of the mouth and of the tentacula, as the Actinice, with 

 an internal organization nearly similar; but it is a com- 

 pound animal, of which the individuals are united on a com- 

 mon base, which either offers to the eye a broad surface, 

 or in the shape of a fleshy wrinkled tube sticks fast to the 

 rocks, and sends forth other fleshy tabes creeping along in 

 various directions. These singular creatures evidently 

 bring us back to the group of Acrita which we left by 

 means of the Tunicata, and the classes into which the 

 animal kingdom may be resolved are thus found to return 

 into themselves. 



