282 Mr. A. H. Hassall's Catalogue of Irish Zoophytes, 



receding tide, among which numerous corallines will be im- 

 bedded, particularly if a high wind have prevailed during the 

 day. Although I have not as yet had an opportunity of car- 

 rying into effect what I here recommend, I am convinced that 

 any individual who would be at the trouble and possessed 

 sufficient resolution to leave a warm fire at this uninviting 

 season, and encounter the rough, but refreshing sea-breeze, 

 would meet with an ample reward for the labour bestowed and 

 self-denial exercised. The fact of the phosphorescence of one 

 species of Sertularia, S. pumila, was, I have lately learned, 

 discovered by Stewart some time since ; but the announce- 

 ment of it did not, it appears, lead to further inquiries into 

 this interesting subject. 



An important distinctive character between Ascidian Zoo- 

 phytes and those of other classes, may be derived from the 

 arrangement of the tentacula. In the Ascidian type of Zoo- 

 phytes the tentacula are arranged in a determinate order, be- 

 ing disposed either in a crescent, as in some freshwater species, 

 or in the form of a bell, as in the marine orders of this class ; 

 whereas in the Hydroid, Helianthoid and Asteroid classes 

 they do not describe any regular figure, but are irregularly 

 disposed around the mouths of the polypi. An Ascidian 

 zoophyte, therefore, may at once be distinguished from all 

 others by observing the arrangement of the tentacula, and 

 without reference to internal organization. It is difficult to 

 conceive anything more strikingly beautiful, on a small scale, 

 than one of these Ascidian Zoophytes viewed under the field 

 of a microscope : the regular and elegant cup-like form de- 

 scribed by the tentacula ; the ceaseless and rapid action of 

 the cilia ; the uniform direction of the current w^hich flows 

 over these, carrying with it numberless revolving particles, 

 some whereof are destined for the little creatures^ sustenance ; 

 and all these, if seen through a strong light, clothed in the 

 brightest prismatic colours, cannot fail to elicit the admiration 

 of the beholder. Should the slightest motion occur to disturb 

 it, the polype instantly withdraws itself within the shelter of 

 its little habitation, at once its home and its grave, and is con- 

 cealed from sight ; its beauties are however again displayed as 

 soon as the agitation of the surrounding water ceases. It is 

 difficult, I say, to conceive a more beautiful or interesting spec- 

 tacle than is furnished by a single polype when thus view ed ; 

 but what must be the appearance formed by the countless 

 thousands of these animals which daily thus display them- 

 selves, peopling cave, rock and pool ! and yet nearly six thou- 

 sand years have elapsed since their first creation before the 

 eye of man rested on them. 



