INTRODUCTION. 27 



were an independent organism as regards its growth, but its membranes are continuous 

 with those of the parent. In many corals the base of the bud and the visceral cavity of 

 the parent are at first contimious ; but in others the membrane reflected over the septa, 

 the margin of the wall, the external surface of the wall or of the base, produces the 

 gemmation. 



The gemmation may take place, then, on any part of a coral. It may occur within 

 the calice, on the calicular margin, on any part of the wall between the calice and the 

 base, and it may happen at the base. The direction of the line of growth of the bud has 

 much to do with the future shape of the corallum, and the power of growth of the parent 

 coraliite after the development of the bud also. 



The parent coraliite may not grow after the production of a bud from its external M'all ; 

 the bad becomes a perfect coraliite, and gives origin to a bud in its turn. This repetition 

 may go on, and a corallum results, formed by an ascending series of simple corallites ; or 

 the parent coraliite may elongate after giving off a succession of whorls of buds which do 

 not in their turn always develop others. The space between the Avhorls and the individual 

 buds becomes filled up with exotheca and coenenchyma. A dendroid corallum results, as 

 in the genera Madrepore^ and Stylophora. 



Again, straight cylindrical corallites give off one or two buds, and all continue to grow, 

 passing upwards, the calices keeping on one level, and the corallites being parallel. This 

 determines the massive corals of many Astrmdce. 



A corallum with geometrical calices whose walls are soldered together buds within 

 the calices f the parent calice and the bud grow, and the coral both expands laterally and 

 increases in height. This produces a very common form of compound coral. 



Certain corals never raise themselves far from the foreign substance they rest upon ; 

 the base gives off a bud, which, stolon-like, gives forth others, and all turn upwards 

 slightly. 



From these considerations it is evident that there is a necessary division of the 

 gemmation into ccdicular, basilar, and lateral. 



Calicular gemmation takes place from the interseptal loculi near the columellary space, 

 and either midway between it and the wall, or just within the calicular margin. One or 

 more buds may grow at once, and the budding may or may not be fatal to the parent. A 

 pseudo-calicular gemmation is occasionally seen in simple corals which are only oviparous. 

 It is produced by one of the young polypes settling on the parent accidentally, and 

 growing to its detriment.^ 



The true calicular gemmation is well seen in the simple forms of the genus Cyatho- 

 pliyllmn^ in a new genus from the Lias {Lepidophylluvi), and in the genera 8taiiria,^ 

 Isastrcea^ &c. 



1 Plate IV, fig. 18. - Plate IV, fig. 11. "" Plate IV, figs. 8, 10. 



* Plate IV, fig. 10. s Plate III, fig. 15. « pi^te IV, fig. 11. 



