504 Mr. II. M. Bernard on the 



hand, only one ring of lateral buds is typically produced by 

 the axial polyp, whicii then apjiears to cease to grow any 

 further, the work of building up the corallum being carried 

 on by the ring of buds. 



If the facts justify this comparison, and I have little doubt 

 but that they do, it follows that the coenenchy ma which streams 

 down round the axial polyp, thickening its walls and sub- 

 merging its lowest and oldest buds, is strictly homologous with 

 the ccenenchyma which in the Tarhinaria streams down to 

 thicken the wall of the axial polyp to form the stalk of the 

 cup and to widen its base of attachment. The structural 

 similarity of the two has been already noted. In Tarhinaria 

 the cojnenchyma connects further the ring of buds, forming 

 with them the wall of the cup, and ultimately the fronds 

 (PI. XIX, fig. 3). Mr. Brook*, led astray by the common 

 belief that the budding in Tarhinaria is quite distinct from 

 that in Madrepora, drew a distinction between the ccenen- 

 chyma in the two genera, which no longer holds good when 

 the respective methods of budding are correctly understood and 

 compared. 



Initial Variations in the Form of the Young Cap. — If the 

 ring of buds rising round the axial polyp is perfectly hori- 

 zontal, the youngest cup is symmetrical ; but if the ring is 

 not horizontal, but forms a wavy line round the axial polyp, 

 then the cup is not symmetrical, but has a wavy edge. 

 Again, if the polyps grow upwards at a sharp angle, the cup 

 is conical or vasiform ; if they grow out at a wide angle the 

 cup flattens and maybe quite disk-shaped or peltate; and, 

 finally, if in growing outwards they bend downwards, the 

 everted cup may easily form a hemispherical mass, the edges 

 of which creej) along the substratum. All these methods of 

 growth take place. 



Second ar^d following Generations of Duds. — We may now 

 temporarily dismiss the axial polyp, whose further fate we 

 shall return to presently ; the question which concerns us is 

 how and when do the radiating daughter-polyps bud, in order 

 to extend the edge of the cup. 



For clearness of description we may assume that, whereas 

 the axial polyp forms a complete ring of buds, each radial 

 polyp produces only a portion of a ring, and that on the side 

 turned away from the axial polyp. 



The process appears, judging from a comparison of many 

 specimens, to be as follows : — As soon as the polyps at any 

 time forming the actual edge of the cup have, by outward 



♦ " Affinities of the Genus Madrej)ora^' .Toiirn. I^inn. Soc, Zool, 

 vol. xxiv. p. 353. 



