374 



SCIENCE 



[N. S. Vol. XXVI. No. 6G4 



we find two clear lines of departure from this 

 form: 



(a) They have become less convex, and growth 

 has gone on round the edges, and the colony has 

 become explanate. 



(6) They have become more convex, and the 

 colonies have become hemispherical and columnar.' 



Each of these types of growth undergoes 

 further modifications. Under (a) two sec- 

 ondary modifications are recognized, one in 

 which small areas by stimulation into rapid 

 budding form irregular columns, that can 

 immediately readopt the explanate method of 

 growth if they come into contact with any 

 body that they can incrust; the other, the 

 edges may run out into lobes, which by curling 

 around form knobs or cylinders, that are left 

 behind on the surface by further growth of 

 the edge. Five variations of the massive 

 growth-form are recognized, the principal ones 

 of which are designated, pulvinate, expanding 

 sheaf formation, and branching. The remarks 

 on growth-form apply to both Goniopora and 

 Porites. 



In Volume VI. the interesting observation 

 is recorded, that metameric growth is usual in 

 poritid corals, i. e., the first distinctive growth 

 form repeats itself in the later development of 

 the corallum. 



Porites differs from Goniopora chiefly by 

 lacking the third cycle of septa. The calices 

 of the genus are bilaterally symmetrical; at 

 each end of the plane of symmetry is a di- 

 rective septum; one directive, the dorsal, be- 

 ing solitary, not taking part in the formation 

 of a septal group, while the opposite one, the 

 ventral, may be free or have a secondary 

 fused to each of its sides; this directive and 

 the two adjacent secondaries are designated 

 the " triplet." 



On each side of the plane of symmetry are 

 two lateral pairs of septa; each pair is com- 

 posed of a primary and a secondary septum 

 fused by their inner ends. The details of the 

 arrangement of the pali have been worked out 

 with care. These structures occur, when the 

 formula is complete, before each lateral pair, 

 at the points of the septal fusion, on the soli- 

 tary directive and on each member of the 



""The Genus Goniopora," p. 23. 



triplet, i. e., there are eight pali. The varia- 

 tions of the palar scheme are numerous. The 

 members of the triplet may fuse together by 

 their inner ends, then a single palus, developed 

 at the point of fusion, stands before the group, 

 reducing the number of pali to six. The pali 

 may be absent from the laterals of the triplet, 

 when they are free from the directive, or they 

 may be present on the laterals but none on the 

 directive; there may or may not be one on the 

 dorsal directive. Those before the lateral 

 pairs are the most persistent, but in deep cal- 

 ices all pali may be obsolete. The elucida- 

 tion of the various types of palar formulae is 

 one of Bernard's most important contributions. 

 Bernard's account of the structure of the 

 septa and wall will next be discussed. He 

 considers that the septum of Porites is com- 

 posed of upright trabeculse, joined together by 

 radial horizontal bars and by tangential bars, 

 the latter known as synapticula. In the ideal 

 calice, there is the vertical columellar tubercle ; 

 outside it, each septum is composed of three 

 trabeculse, which, named in order from the 

 center outward, are the palar, the septal and 

 the mural. These trabeculse by projection on 

 the septal margin produce respectively the pali, 

 the septal granules and the mural ridge. 

 When the calices are crowded, the mural tra- 

 beculse of adjacent calices may alternate in 

 position with each other and produce zigzag 

 walls. In the ideal calice there is only one 

 septal trabecula, and consequently only one 

 septal granule between the palus and the wall 

 for each septum. Sometimes, however, there 

 appear to be two granules, corresponding to 

 two trabecula, between each palus and the ap- 

 parent wall, the outer trabeculse being joined 

 by a synapticular ring. Bernard here con- 

 siders that there is only one septal trabecula, 

 the one next the palus, and that the next outer 

 trabecula is in reality the wall trabecula; the 

 third trabecula outward from the palus is 

 homologically to be regarded as costal. These 

 homologies of Bernard are based upon the as- 

 sumption that the trabeculse of Porites are 

 parallel in their courses, and in general per- 

 pendicular to the outer surface of the coral- 

 lum, an assumption with which the reviewer 



