. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. MORPHOLOGY OF THE MADREPORARIA. 33 retians the bilaterality of development of its septa; while in the other the bilateral symmetry of growth becomes replaced by a radial disposition of the parts. Whenever alar fossulre are present they represent an incompletion in the establishment of the newer septa of the alar region, as compared with species in which no alar fossulae are represented ; they have only a develop- mental significance, and would not correspond with any structural peculiarity of the fully developed polyp. As wo
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. MORPHOLOGY OF THE MADREPORARIA. 33 retians the bilaterality of development of its septa; while in the other the bilateral symmetry of growth becomes replaced by a radial disposition of the parts. Whenever alar fossulre are present they represent an incompletion in the establishment of the newer septa of the alar region, as compared with species in which no alar fossulae are represented ; they have only a develop- mental significance, and would not correspond with any structural peculiarity of the fully developed polyp. As would naturally be expected from such an explanation even individuals of the same species may vary much with regard to the presence or absence of alar fossulae. In the calice of some specimens of Microcyclus discus, for example, there is a distinct grouping of the alar septa,. FIG. 6. A corresponding second pair of septaT() has appeared within the ventro- lateral chambers. while in others the septa have become perfectly radial, and no alar region is distinguishable. The alar fossulae represent regions where new septa are being added, and the interspaces may reasonably be expected to be different from the other septal interspaces, and likewise to vary at different stages according as the new septa are just appearing or are nearly fully developed. From developmental studies the conclusion is thus reached that in all ordinary species of zaphrentoid corals the septa of the alar region pass through a fossular stage as here understood,. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Marine Biological Laboratory (Woods Hole, Mass. ); Marine Biological Laboratory (Woods Hole, Mass. ). Annual report 1907/08-1952; Lillie, Frank Rattray, 1870-1947; Moore, Carl Richard, 1892-; Redfield, Alfred Clarence, 1890-1983. Woods
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