Mr. A. H. Hassall on some new Irish Zoophytes. 483 



L. — Description of two new Genera of Irish Zoophytes^, By 

 Arthur Hill Hassall, Esq., Corresponding Member 

 of the Natural History Society of Dublin. 



Order ZOOPHYTA ASCIDIOIDA. 



Family A L c Y o N I D u L ^. 

 Genus Cycloum. 

 Character. — Polypidom fleshy, encrusting, covered with numerous 

 imperforate papillae : polypi ascidian ; ova in clusters. 



Cycloum papillosum. — Polypi with eighteen tentacula disposed in 

 the form of a bell. 



This species is almost invariably found investing the frond 

 of Fucus serratus, over the surface of which it spreads in 

 patches of from one to two inches in extent, more frequently 

 of one, and seldom exceeding two inches. The crust is fleshy, 

 and rather thick : it is covered with numerous papillae very 

 closely set together. The polypi do not issue from these pa- 

 pillae, which are imperforate, but from larger eminences of 

 irregidar form and size, in the centre of which a puckered 

 depression is seen. The polypi have eighteen tentacula, de- 

 scribing a cup or bell. The ova lie in clusters, each cluster 

 containing six or seven ova arranged in a circle. The clusters 

 are irregularly scattered through the polypidom, and each is 

 inclosed in a space somewhat larger than is sufficient to con- 

 tain it, the remainder of the space being occupied by a fluid 

 in which numerous small particles are seen which are kept in 

 constant action by the motion of the cilia on the ova. Each 

 ovum is of a circular form> but is depressed, one side more so 

 than the other : round its edge a fringe of cilia is apparent ; 

 these may be seen in motion long before the ova are ready for 

 becoming disengaged. I have discovered in this, as well as 

 in the succeeding and some other genera, a body of a very pe- 

 culiar nature, but concerning the uses of which I can at pre- 

 sent only hazard some conjectures. It is, in this species, and 

 in Alcyonidium gelatinosum and hirsutum, in which I have 

 also met with it, of an oblong form, and composed of a trans- 

 parent matter, in which numerous small dark brown granules, 

 circular in shape and not unlike ova, are imbedded. I at first 

 imagined that they were nothing more than particles of lime 

 lodged in a soft jelly-like substance, but this opinion was dis- 

 proved by the application of hydrochloric acid, which did not 

 cause effervescence. These bodies are far more numerous than 

 the ova, and are not more than one-tenth their size. The most 

 probable conjecture which I have been able to form as to 



* Communicated to the Dublin Nat. Hist. Society, Feb. 1841. 

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