MEMOIRS OF THE NATIONAL A(L\DEMY OF SCIENCES. 499 



inside in recrard ti) the axis of the braneh. In this way the axial and abaxial rehitions are 

 established. 



Dr. G. H. Fowler (1887, p. 12) has contributed some In-ief notes upon the budding- of 

 Miiih'epara anpera (Dana), founded upon an examination of the soft tissues of the developing 

 lK)lyps at the apex of the branches, while G. von Koch, in his paper "Die ungeschlechtliche 

 Vermehrung (Knospung und Stockbildung) von Madrepora," 1893, has made an important 

 study of the same sut)ject, but more particularly with regard to the skeleton. The short account 

 of Fowler indicates that the stomo(keum 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 stomodaHun being established 

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

 in the West Indian Madrepora. 



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

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

 corresponding numljer 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 Pontes, as in Madrepora, the full complement of twelve 

 protocnemes is produced at a very early stage and before the tentacles make their appeai-ance. 



BUPDING IN SOLENASTR^A. 



Ainong Astrsean colonies, such as OrhiceUa and Solenastrma, new polyps may l)e 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 colonies of Solenastrsea are already' separated from 

 adjacent polyps on the inner side hy 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 details 

 represented on PI. XII, figs. 86-90. 



Through the transparent tissues eight pei-fect mesenteries were seen to be already developed, 

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

 stomoda'al region of the column wall. All the protocnemes are present, but only the eight 

 Edwardsian mesenteries are yet complete, while in the exocoele on each side of the dorsal 

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



The section represented in fig. 87 reveals the conditions at the level at which the l)ud 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 

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

 V 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 comnmnication between 

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

 added on the upper pai't of the section, represent the exsert septa, the polyp })cing in an expanded 

 condition; the entoccelic septa are large and the exocoelic small. No continuity between the 

 mesenteries of the ])ud 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. 88 is taken from the region of the polyp wholly embedded in the corallum, except for 

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



