28 F. D. Longe — Oolitic Polyzoa. 



altliougli he gives a full account of all the forms of which he treats, 

 makes no mention of them. It is clear, I think, that they were not 

 discovered, or, at all events, taken any notice of, until long after 

 the principle of classification in question was established. Their 

 discovery would not necessarily interfere with the classification of 

 the living Polyzoa, as the living forms classed as Cyclostomata are 

 generally sufficiently distinguished by their calcareous constituency, 

 and the simple tubular shape of their characteristic cells, from most, 

 if not all, of the living families classed as Cheilostomata ; but it 

 does directly challenge the soundness of the principle on which this 

 division is based. 



This definition of the Cyclostomata can only be reconciled with 

 the existence of these operculoid features in the Diastoporidcn, if, 

 notwithstanding their apparent homology with the opercula of the 

 Cheilostomata, these lids have really some function and raison-d'etre 

 altogether different. But, if we refer to Professor Busk's and Mr. 

 Hincks's account of the recent Diastoporidcs, we shall see that they 

 offer no satisfactory reasons whatever for distinguishing these lids 

 from the opercula of the Cheilostomata. 



In his description of Diastopora patina,^ Professor Busk thus 

 refers to the two kinds of cells presented by this form : " Central 

 cells immersed, and usually closed, marginal ones erect and open." 

 As to the nature of the lids by which the central cells are closed, 

 Professor Busk offers no suggestion. 



In his account of the same species, Mr. Hincks thus describes the 

 cells : " Zocecia stout, minutely punctate, crowded ; in the central 

 portion of the colony immersed and closed, disposed in radiating 

 lines ; towards the margin usually erect, open ; orifice in the central 

 cells sub-elliptical, plain; in the marginal cells, sub-orbicular."^ As 

 to the closed cells, Mr. Hincks observes : " It is difficult to deter- 

 mine what is the precise function of the closed cells which occur in 

 such numbers in every colony. Smitt has suggested that they may 

 be connected with the production of spermatozoa, and notes that in 

 Tnbidipora patina there is sometimes a small tubular opening in the 

 cap or operculum analogous to the projecting process in Diastopora 

 Sarniensis. It may be objected to this view that the closed cells 

 are so numerous as to be out of all proportion to the function assigned 

 to them, but it would be difficult to suggest a better interpretation, 

 and it will do good service by giving direction to inquiry."^ 



In his account of J). Sarniensis, Mr. Hincks thus describes the 

 cells : " Zooecia stout, generally free and sub-erect for a considerable 

 portion of their length; orifice elliptical, occasionally closed by an 

 opercxdum, from the upper part of which a small tube projects." ■* As 

 to the operculate cells, he says : " The precise significance of the 

 zooecia (some of which are to be met with in each colony), which are 

 operculate and furnished with a small tubular process at the top, is 

 unknown. They have been conceived to be subservient to repro- 



1 Catalogue of the Cyclostomatous Polyzoa in the British Museum. 



2 British Marine Polyzoa, p. 458. 



3 Ibid. p. 460. * Ibid. p. 463. 



