CCELENTERATA : ZOANTHARIA. 



163 



gemination. In this mode of increase the original polype throws out buds 

 from some point on its sides between the base and the circle of tentacles, 

 and these buds on becoming perfect corallites may repeat the process. 

 This is one of the commonest modes of growth amongst the recent corals, 

 and it gives rise chiefly to dendroid or tree-like corals. 



Fig- 77. Astrcea pallida, a compound sclerodermic Coral, in its living condition. 

 (After Dana.) 



(2.) Basal gemmation. In this method the original polype gives forth 

 from its base a rudimentary coenosarc, from which new buds are thrown up, 

 and which may have the form of foot-like prolongations or of a continuous 

 horizontal expansion. The resulting 

 coralla are usually massive or encrust- 

 ing, and the youngest corallites are, of 

 course, those placed on the periphery 

 of the colony. 



(3.) Calicular gemmation. This con- 

 sists in the production of buds from the 

 calicine disc of the parent corallite, 

 which may or may not continue to grow 

 thereafter, whilst the new corallites thus 

 produced generally repeat the process. 

 This mode of growth is exceedingly rare 

 amongst the Zoantharia sclerodermata, 

 and is never typically exhibited ; but it 

 is a characteristic feature in many of the 

 Rugose corals. In many of these (fig. 

 78), the original polype throws up from 

 its calicine disc one or more new coral- 

 lites, which kill the parent. These, in 

 turn, produce others after a similar fa- 

 shion, till the entire corallum assumes 

 the form of an inverted pyramidal mass 



resting upon the original budding polype. In other Rugose corals the 

 calicine disc gives off but a single bud, which may repeat the process in- 

 definitely till the corallum presents the appearance of a succession of in- 

 verted cones placed one above the other. 



Fig. 78. Calicular gemmation as seen 

 in Lonsdaleia JJoriformis. Car- 

 boniferous. 



