460 TUBULTPORIDjE. 



thin circular base, on which is placed the cclliferous disk, 

 either flat above, with the zooecia wholly immersed, or de- 

 pressed in the centre, and with a raised border of erect 

 cells occupying the margin. In this state D. patina bears 

 a much closer resemblance to its congeners than in its 

 caliculate form (Plate LXVI. fig. 5). 



Occasionally this species assumes a proliferous habit, 

 and produces gemmae freely. From Torbay and from 

 deep water off the Cornish coast, I have obtained very 

 beautiful specimens in this condition, bearing a number of 

 young on the margin of the cup. In one case as many as 

 five are present, occupying a large portion of the edge of 

 the disk. The buds are developed just within the basal 

 lamina on the cellular border. 



In the finest proliferous specimens the cup is deep and 

 funnel-shaped and stands erect, being attached by a very 

 small portion of the base. It presents the same character 

 in the Discosparsa maryinata of D'Orbigny, which seems 

 to be merely a proliferous form of the present species. 



In some cases a thin calcareous crust involves the free 

 and erect portion of the marginal cells, and forms a con- 

 tinuous inflation round the disk, which represents the 

 oo3cium. 



It is difficult to determine what the precise function 

 may be of the closed cells, which occur in such numbers 

 in every colony. Smitt has conjectured that they may be 

 connected with the production of spermatozoa, and notes 

 that in T. patina there is sometimes a small tubular open- 

 ing in the cap or operculum, analogous to the projecting 

 process in D. Sarniensis*. It may be objected to this 

 view that the closed cells are so numerous as to be out of 



* Busk mentions " u minute central perforation " as occurring in the cal- 

 careous lid with which the cells arc furnished in Mcsentcripora (' Crag 

 Polyzoa,' p. 1 10). 



