230 ZOOPHYTES. 



formation on both the simple and compound genera, contained in the works 

 of M. Savigny and M. Milne Edwards, together with the notices by Mr 

 Lister in the Philosophical Transactions for 1834. 



Whoever views the Ascidian tenant of zoophytes, will be forcibly im- 

 pressed with the noted difference of its whole appearance, nature, and 

 habits, from those of the animal just referred to. It is full of life and viva- 

 ceous activity, readily quitting that retreat wherein its numerous tender 

 flexile organs are temporarily contracted, for security. The gentlest touch, 

 even modifications of the intensity of light, are sufficient for the display of 

 acute sensations. It can manifestly exhibit its apprehension of danger 

 and its conviction of safety. Its numerous parts are shewn in rapid mo- 

 tion, as if in quest of sustenance, and the exercise of some of the vital 

 functions may be occasionally discovered, while its most prominent orga- 

 nization is subject to continual and instant changes. 



Thus the nature of the product is very different, it is almost directly 

 opposed to that of the Ascidia proper. 



The inorganic portion, that is the polyparium, foundation or dwell- 

 ing of some Ascidian zoophytes, admits of narrow comparison with that of 

 the hydraoidal race. Possibly on a very comprehensive view, a parallel 

 might be found in the majority. But others, in this country at least, 

 ])resent much variety both in form and substance ; and we seem as yet to 

 be in absolute ignorance of the real connection or relation of the different 

 ])arts with each other. 



The elements compounding that portion and the arrangement of 

 the parts, seem more numerous. These elements, to consider them gene- 

 rally, are membranaceous, gelatinous, or calcareous : they appear in flat- 

 tened surfaces, elevated in tubular cylinders, rising in lobate masses, or in 

 a foliaceous form, besides assuming fistulous shapes not remote from those 

 of the Sertularia;. 



From this variety naturalists have endeavoured to frame a vocabulary 

 or a kind of descriptive nomenclature, significant of the form of the dwell- 

 inof, combined with the structure of the tenants. But the obstacles to 

 their design, so excellent and so laudable in itself, prove almost insur- 

 mountable. Until common consent shall determine what is to be held a 



