Proceedings of the Scientific Meetings of the Zoological Society of London 1867

Page 58

1867.] DR. J. S. BOWERBANK ON HYALONEMA MIRABILE. 33 are all of the same species, and that the basal mass and the spiral cloacal organ are truly parts of the same individual. The external mammillated coriaceous dermis of the cloacal system in the dried condition closely embraces the spiral column of spicula, but I could not detect any organic connexion between them. It is probable, from its reticulated structure in some parts, that there was a considerable intervening space between the spiral column and the external envelopment while in the living state, and that the pre­sent condition is due to the contraction of the coriaceous coat while drying. DESCRIPTION OF PLATES IV. & V. PLATE IV. Fig. 1. Hyalonema mirabile iu the cabinet of Capt. Charles Tyler, having a small basal mass of sponge covered with the dermal membrane, which is continued up the spiral column, and from which protuberant oscula are put forth. Natural size. Fig. 2. A specimen of the same species of Sponge presented to me by Mr. H. Lee. The basal mass of sponge is without the dermal membrane, but having the commencement of the corium corresponding with the distal end of the spongeous mass. Natural size. Fig. 3. A section at right angles to the long axis of one of the oscular organs, just below the corrugated terminal disk, exhibiting a view of the inte­rior of the upper portion of the dissepimental form of the complicated valvular structure within the apical termination of the oscular tube. The central membrane containing the natural orifice is slightly in­volved, showing on its outer surface a portion of the sand imbedded. By direct light, magnified 50 times linear. Fig. 4. The lower portion of the valvular structure of the same section, showing the inner diaphragm, or valve, with its motive filaments. The valve partly open, and its membranous structure having a cruciform spicu­lum imbedded in its substance at a. By transmitted light in Canada balsam, magnified 50 times linear. Fig. 5. The apical termination of one of the oscular tubes cut off immediately beneath the corrugated apex, after maceration in solution of potass, showing the circular arrangement of the motive fibres of the outer valve of the osculum in situ, and the attachment of their apices to the outer margin of the central oscular membrane, their basal portions curving downward at the outer margin of the corrugated apex of the organ to their respective basal attachments. Mounted in water and viewed by transmitted light, magnified 50 times linear. PLATE V. Fig. 1. One of the lamellse of the skeleton from the basal mass of sponge of Hyalonema mirabile in the British Museum, exhibiting the general structure of the skeleton and the mode of disposition of the fimbriated multihamate birotulate spicula, the spiculated cruciform, and the various forms of interstitial spicula. a. One of the largest of the at-tenuato- rectangulated hexradiate interstitial spicula in situ, with a group of three fimbriated multihamate birotulate spicula, and spicu­lated cruciform spicula dispersed on the transparent interstitial mem­branes, b. Skeleton-fasciculi, with a row of spiculated cruciform spicula based on one of them. Magnified 50 times linear. Fig. 2. A fimbriated multihamate birotulate interstitial spiculum of the primary system. Magnified 175 times linear. Fig. 3. An elongo-recurvate dentato-birotulate interstitial spiculum of the se­condary system. Magnified 308 times linear. PROC. ZOOL. Soc-1867, No. III.