545 



add, that I also employed M. Poinsot's beautiful theory of 

 couples, which has introduced so much clearness into the 

 fundamental doctrines of mechanics. 



Mr. G. Wilkinson read a paper on the existence of the 

 pointed arch in the early buildings of Ireland, prior to the 

 introduction of Gothic architecture. 



Mr. Petrie offered some remarks on Mr. Wilkinson's com- 

 munication. 



Dr. Allman noticed the occurrence in Ireland of Frederi- 

 cella Sultana, and entered into certain details of its zoological 

 and anatomical characters. This zoophyte has been very 

 imperfectly described, and is moreover burthened with a dis- 

 cordant synonomy which has involved its history in no small 

 obscurity. The difficulty which is thus necessarily con- 

 nected with the attempt to determine the true Fredericella 

 Sultana, Dr. Allman endeavoured to remove, by reducing to 

 some sort of oi'der the mass of synonymes in which it is in- 

 volved. It would appear to be the Tubularia Sultana of 

 Blumenbach, its original discoverer; the Plumatella Gelat- 

 inosa of Dr. Fleming ; the Plumatella Sultana of Sir J. G. 

 Dalyell ; and the Fredericella Sultana of Gervais. It would 

 appear also that the zoophyte described by Mr. Varley, in a 

 late number of the London Physiological Journal, is the 

 same as the present. 



By some singular oversight, Dr. Fleming, in the descrip- 

 tion of his Plumatella Gelatinosa, refers to the Tubularia 

 Gelatinosa of Pallas, described in the " Elenchus Zoophy- 

 tarum." The Tubularia Gelatinosa of the Elenchus, how- 

 ever, is quite a diflerent animal ; it belongs to the group with 

 crescentic disks, and is identical with the free variation of 

 Plumatella repens. 



The author, in entering into the details of its anatomical 

 structure, drew attention to the high ascidifoi'm type which 



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