FLUSTRA. 27 



CHArTEU II. 



INVESTING ASCIDIAN ZOOPHYTES. 



If the various classifications proposed by authors be exposed to ani- 

 madversion, it is from the insufficiency of the characters adopted. None 

 are so definite and exclusive as to prove the permanent foundation of 

 many of the different sections. 



Naturalists may prefer some of various features, by the combination 

 of more than one, as their predominant guide. They may select the form 

 and the substance of the polyparium, the figure or position of the cell, the 

 genus of the hydra by which it is occupied, or the mode of perpetuation. 

 Each of these may be assumed at will, according to their importance in 

 the view of observers. All are prominent features. 



But they are not such as to exclude others, which the learned will deem 

 alike important in detail, or perhaps paramount to the rest. Hence do 

 different and sometimes very incongruous arrangements ensue, which may 

 be of difficult or equivocal correction, until common consent shall inter- 

 pose an authority for the characters to be chosen. 



Some of the zoophytes are so intimately connected, by corresponding 

 organization, that their kindred is undisputed. Simple inspection decides 

 the question, but protracted study makes us waver. The hydra of the 

 fresh waters, and the Hydra tuba of the sea seem in the nearest alliance 

 from aspect and habits. But patient investigation proves their ultimate 

 nature, separated by an insurmountable chasm. The Sertularia, the 

 Virgularia, and the Medusa, all perpetuate their race through the medium 

 of a planula. No products can have less reciprocal resemblance than 

 the respective parents. The preceding Flustrse are allied by their folia- 

 ceous formation, by leaves of cellular structure, and in originating from a 



