POLYIIPERA. 469 



and with a rapid, but not $eep incision, lay open the 

 envelope from the outside ; a series of convoluted bands 

 will bulge through the opening, but if these are quickly 

 brushed aside, certain lobular or grape-like masses will be 

 perceived, darker in colour, and almost entirely hidden by 

 these bands, but growing from the wall of the envelope. 

 They do not appear to have a fixed locality, as they may 

 be found near the base, about the centre, or close to the 

 disc ; it is, therefore, sometimes necessary to make three 

 or four incisions before detecting them; once seen, they 

 will be easily distinguished from the convoluted bands, 

 although very difficult to remove them without removing 

 some of the bands." 



The manner in which the aggregation of zooids, consti- 

 tuting a compound coral, is developed from the primarily 

 solitary Actinozoic embryo, exercises an all-important 

 influence upon the form of the Corallum. Sometimes, as 

 in most Turbinolidce, neither gemmation nor fission ever 

 take place. In the Oculinidce, gemmation alone occurs, 

 and in these and other Actinozoa, the development of buds 

 takes place either from the base or from the sides of a 

 corallite, cr from the coenosarc. Certain of the extinct 

 Rugosa, however, exhibit calicular gemmation, the buds 

 being developed from the oral disc or cup, which can 

 hardly have retained any active vitality. The massive 

 coralla of some Cyathophyllidce } thus standing like inverted 

 pyramids, all the buds supported upon the narrow surface 

 of the primary zooid, have a very singular and striking 

 aspect. The Beroidce appear at first to differ very widely 

 from the type of structure which prevails among the 

 other Actinozoa, but a close examination of any of their 

 forms suffices to demonstrate the justice of the conclusion 

 advocated by Frey and Leuckart, as to their essential 

 identity with Actinia. The Cydippe, which abounds upon 

 our own coasts, affords, from its small size and extreme 

 transparency, an excellent subject for the student of Be- 

 roidce. It is impossible here to enter into the varieties 

 of form presented by the Beroidce, and which chiefly arise 

 from the development of lateral lobes, a process which is 

 carried to so great a length in Cesium that the body 

 becomes ribbon-like. The Beroidce and the Actinidce 



