some Sjyecies o/* Madrepora. 193 



wall, the small perforations in it are direct communications 

 between the so-called parent and the cavity of tiie bud ; but 

 when the bud arises from the top of many layers of mural 

 tissue the interspaces in the sclerenchyma do not by any means 

 form a direct communication between the two cavities. In 

 fact no sucli communication exists, except in a very indirect 

 manner, and through the medium of the dermal structures. 



In the transverse sections through an axial corallite and 

 some surrounding buds, these can often be traced to the outside 

 of the original or first wall of the apical corallite, wnth wliich 

 they communicate through the ordinary pores, and it may be 

 noticed that a quantity of exogenous sclerenchyma surroundss 

 the bases of the buds. 



The hood of the bud having attained the length and breadth 

 of 0*5raillim., faint traces of costre are to be seen upon it, and 

 these delicate laminse often take the line of the costaj, which 

 are towards the base of the parent corallite. At this stage 

 there is not a trace of a septum within the bud. 



The formation of the trabeculate wall occurs first of all, 

 then costce begin to develop, and it is not until the bud has 

 ^npreased in length that traces of septa are 1o be seen. 



The first sign of a septum is a row of delicate spinules, and 

 it passes straight down the inside of the bud, commencing 

 at some distance, howeycr, from the opening. There may be 

 two rows of spinules, or traces of all the primaries may be- 

 pome apparent almost at the sam.e time. One row is almost 

 invariably larger than the others, and is placed towards the 

 outer part of the cavity, or rather at the remotest point from 

 the wall of the parent. 



The next phase of growth is the elongation of the bud, tlie 

 forward growth of the fiiture calicular opening by production 

 of the terminal trabeculas. This is followed by a growth 

 upon the parent wall in front of the hood-like structure, and, 

 the completion of the circle of the calicular opening, the bud 

 thereafter growing with its front or forward part free from the 

 parent, from which it gradually diverges in direction. 



As growth proceeds the young corallite increases slightly 

 in size and breadth, and a little more mural tissue is usually 

 developed on the outer lip of the calicular opening ; but still 

 the septa are deeply seated, and all except the larger or the 

 two opposite primaries, are minute and spiniform. Very fre- 

 quently the two larger and opposite septa become lamellai-, 

 from the growth of calcareous matter between the spinules, 

 and the four other primaries remain very slightly developed 

 and still spinulose in character. 



There are more costge than septa, and they do not always. 



