MINUTE STEUCTUllE OF STEOMATOPOKA AND ITS ALLIES. 237 



FiftliJij. The stellate systems of water-canals, so commonly, 

 though not universally, present in the Stromatoporoids, are appa- 

 rently believed by Mr. Carter to correspond with the branched 

 grooves and cojnosarcal stolon-like tubulation which he has 

 described as cliaracterizing the surfaces of the layers of the 

 crusts of Hydractinia. We are unable to accept this view, upon 

 the ground that the radiating water-canals of the Stromato- 

 poroids, though sometimes superficial, especially where arranged 

 round a superficial eminence, more commonly pass obliquely 

 through the successive laminae and interlaminar spaces, per- 

 forating these, as several of our preparations show, one after the 

 other, and not lying in the plane of any particular lamina. 



Sixth! I/. One of the Stromatoporoids which Mr. Carter has 

 examined (Ann. & Mag. Nat. Hist. ser. 4, vol. xix. pi. viii. 

 figs. 22, 23), and from which he has drawn important conclu- 

 sions supporting his views, appears to us to be a member of the 

 aberrant and still imperfectly understood genus Caunopora'^, or, if 

 not so, to be a specimen in which a colony of Stromatopora has 

 grown round and enveloped a colony of the coral Syringopora. 



6. To Polyzoa. — "We have already intimated {antea, p. 190) 

 that the idea of the affiliation of Stromatopora to the Polyzoa is 

 not new, since the two Sandbergers and Eerd. Eoemer (1850- 

 1856), for the reasons heretofore given, held this view. Apart 

 from their interpretation of the structural resemblances, we have 

 brought to bear examinations and comparisons on our own behalf. 

 Among an extensive series of recent and fossil Polyzoan forms 

 investigated by us with reference to the question at issue, we have 

 been particularly struck by a good examj^le of EscJiara nohilis, 

 Michelin. This specimen, from the Upper Grreensand, was an 

 ovoid mass several inches in diameter, externally irregular, rough- 

 ened, and scaly, but with no elevations, perforations, or other- 

 wise special outward resemblance to the Stromatoporoids. A 

 vertical section through its middle dis2)layed a small foreign body 

 as a nucleus, around which, like the coats of an onion, in regular 

 successive layers, about six to a line in depth, the tiers of zooidal 

 cells were ranged. Thus this vertical section — what with the walls 

 of the zocecia so built up as to represent horizontal or concentric 

 laminae and vertical or radial pillars, the cells themselves resem- 



* Quite recently, while this is passing through the press, Mr. Carter himself 

 announces his mistake and admits his supposed Stromatopora to have been ^ 

 Caunopora placenta (Ann. & Mag. Nat. Hist., July 1878). 



17* 



