1895.] Study of Madreporarian Typ^s of Corals. 



11 



trical around ideal trabecular axes in the median septal plane. Eacli 

 member of a successive series of fascicle "pairs" or " groups" in 

 a trabecula is called by the author a trabecular part (Trabekelglied) . 

 The " fascicle " may be regarded as the structural unit of the coral 

 skeleton. Two or more fascicles combine to build up a 11 trabecular part." 

 And the differences in the relative arrangement of trabecular po,rts deter- 

 mine the endless varieties of skeletal form within the Madreporaria. 



The author has subjected the following typical genera to a detailed 

 microscopic investigation : — Galaxea, Mussa, Heliastraea, Groniastraea, 

 Montlivaltia, Thecosmilia; then Fungia, Siderastraea, Lophoseris ; 

 further, Eupsammia, Haplarasa ; and, lastly, Turbinaria, Actinacis, 

 Madrepora, and Porites. This research enables the author to state 

 that different types of septal structure are characteristic of different 

 groups of Madreporaria. The differences relate to the microscopic 

 structure of the trabecule and to the arrangement of trabe- 

 calfe in the plane of a septum. Ifc is impossible here to 

 do more than indicate the line of research. Turbinaria is an 

 example of an extremely simple structural type. The component 

 trabecules are small, -uniform in size, and directed all in the same 

 way, obliquely or almost horizontally inwards from the periphery of 

 the septum to the inner edge. The fascicles are paired, and their 

 axes never bend out of the median septal plane. Galaxea has a 

 septum whose trabecules bend right and left from a definite area of 

 divergence in the septal plane. The individual trabecule are large, 

 vary in size, and the axes of the paired fascicles bend out of the 

 median plane towards the opposite surfaces of a septum. The 

 septum of Mussa is composed of a number of broad ridges, elliptical in 

 section, and ending at the upper edge of the septum in broad "spini- 

 form teeth." The author shows that each " spiniform tooth " is itself 

 finely serrated, and that the serras represent apices of trabecules. In 

 short, a single broad ridge of the Mussa septum is the precise homologue 

 of the complete Galaxea septum, being built up of fan-shaped groups 

 of trabecules diverging right and left from the middle area of a ridge. 

 Again, Fungia has, like Mussa, a septum composed of a number of 

 ridges, but the trabecules in each ridge have a coarse almost parallel 

 with one another. The emergent fascicles are thus so close that 

 coalescence inevitably takes place; the soft parts of the polyp 

 clothing the ridge are pushed outwards at the prominent middle 

 part of the ridge, and readily give rise to synapticular union between 

 septa. Further reference to this part of the work must be omitted 

 here. 



The author observed in sections of recent types that a larger 

 amount of organic cell-material was usually present near the 

 median plane of the septum than towards the lateral surfaces. This 

 she believes may be attributed to the greater rapidity of the calca- 



