MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 499 



inside in regard to the axis of the branch. In this way the axial and abaxial relations are 

 established. 



Dr. <i. 11. Fowler (1887, p. L2) has contributed some brief notes upon the budding of 

 Madrepora aspera (nana), founded upon an examination of the soft tissue- of the developing 

 polyps at the apex of the branches, while (i. von Koch, in his paper " Hie ungeschlechtliche 

 Vermehrung (Knospung and Stockbildung) von Madrepora," L893, lias made an important 

 study of the same subject, hut more particularly with regard to the skeleton. The short account 

 of Fowler indicates that the stomodseum is invaginated to a considerable depth into the future 

 polyp cavity before it is perforated, and also apparently before any mesenteries arise. The first 

 mesenteries, already bearing filaments, are formed from the walls of the canals, apparently 

 independently of the rest of the polyp, the connection with the stomodseum being established 

 later. The process of gemmation in Fowler's species is thus altogether different from that 

 in the West Indian Madrepora. 



Many attempts have been made to obtain the early stages in the gemmation of Porites, 

 tint without any material results. Sections through polyps with six or eight tentacles show a 

 corresponding number of complete mesenteries, but the remaining members necessary to 

 make up the normal six pairs are also present, though not developed to the same degree as 

 in older polyps. It may be that in Porites, as in Madrepora, the full complement of twelve 

 protocnemes is produced at a very early stage and before the tentacles make their appearance. 



BUDDING IX S0LENASTR2EA. 



Among Astrsean colonies, such as Orbicella and Solenastraea, new polyps may be either 

 intercalary or marginal in origin. By means of the latter the colony spreads laterally, while the 

 intercalary buds serve to occupy the larger superficial area as the colony rises in height. 



The earliest marginal buds observable in colonics of Solenastraea are already separated from 

 adjacent polyps on the inner side by an external groove, while the outer side, forming the 

 periphery of the colony, is necessarily independent of other polyps. Sections made through one 

 of these marginal buds, preserved in the expanded condition, reveal at different levels the detail- 

 represented on PI. XII. tigs. 86-90. 



Through the transparent tissues eight perfect mesenteries were seen to tie already developed. 

 but no tentacles were yet apparent. Fig. 86 is from a transverse section through the free 

 stomodseal region of the column wall. All the protocnemes are present, but only the eight 

 Edwardsian mesenteries arc yet complete, while in the exoco?le on each side of the dorsal 

 directives the rudiments of a pair of second-cycle mesenteries (A, A) are visible. 



The section represented in tig. 87 reveals the conditions at the level at which the bud is 

 connected with the mother polyp on the inner side, but is free on its outer aspect; from the 

 arrangement of the mesenteries the outer side is seen to be the sulcar or ventral aspect, and the 

 inner the sulcular or dorsal border. The eight Edwardsian mesenteries alone bear mesenterial 

 filaments, and the retractor muscles are sufficiently well developed to enable the pairs of directives 

 to be determined. The pairs of metacnemes within the sulculo-lateral exocteles are better 

 developed than in the previous figure, and another pair (B) has appeared in the left middle lateral 

 exoccele. but the corresponding pair on the right side is undeveloped, and at this stage mesentery 

 Y has nearly disappeared on the same side. The. boundary wall between the bud and the fully 

 developed polyp is perforated in a number of places, and by this means communication between 

 the gastro-ccelomic cavity of each is permitted. The portions of the skeleton of the adult polyp, 

 added on the upper part of the section, represent the exsert septa, the polyp being in an expanded 

 condition: the entocoelic septa are large and the exoccelic small. No continuity between the 

 mesenteries of the bud of the adult polyp are represented in this or any of the sections. To the 

 right, at the angle between the wall of the bud and the adjacent polyp, are the first indications of 

 another bud. 



Fig. ss is taken from the region of the polyp wholly embedded in the corallum, except for 

 a limited area on the right upper side; the bud polyp is now entirely separated from that 



