Report on the zoological collections made in the Indo-Pacific Ocean ...

BPONGIIDA. 391APLTSINID^.Aplysinida, Carter, Ann. S^- Mag. N. II. (o) xvi. p. 132.This name is used in a wider sense than that to which Vosmaer(Mitth. Zool. Neapel, iv. p. 444) limits it.19. Aplysina membranosa.Spongia membranosa, Pallas, Elench. Zooph. p. 398.Spongia membranacea, Esper, Pflanzentlt. ii. p. 2-")G, pi. xxxiv.? lauthella conceiitvica, Hijatt, Mem. Bost. Soc. ii. p. 407.? Aplysina purpurea, Carter, Ann. i^- 3Iaff. iV. H. (o) \i. p. 36.A very fine species, fortunately preserved in spirit as well as in thedry state. It forms a cylindrical mass, which has the same generalform as that given in Esper s figure (/. c.) ; the base of the wetspecimen is about 40 millim. (l-|iuch) in diameter. The dry specimen,which is much the largest of the two, is 580 millim. (22^ inches)high, and the maximum diameter, which is at about 5 inches abovethe base, is about 40 millim. (13- inch). At 77 millim. (3 inches)above the base a branch is given off, 22 millim. (g inch) in maximumdiameter and 145 millim. (9| inches) in length, and on the sameside, about 30 millim. higher up, a smaller branch, 12 millim.(^ inch) in maximum diameter and 75 millim. (3 inches) in height.The skeleton consists of a very open and irregular network of fibres,1*5 to 2 millim. in thickness, which arise at the base of the sponge,and take a longitudinal but somewhat sinuous course along the interiorof the cylindrical column of which the sponge consists. Theythrow out branches somewhat freely from their sides, and subdivideterminally into ramifying branches ; the resulting twigs anastomosefreely, the superficial ones end in outwardly and upwardly directedpoints, usually bi- or tri-furcate, which are just covered by thetough dermis ;the apices are -18 to '28 millim. in diameter. Thedermis and the internal membranes consist of a tough membraneof a puce or dull purple colour in spirit, almost black in the dry state.The membrane is seen with the naked eye to be marked with numerousraised thickened lines, which radiate from the projecting apicesof the dermal conuli (formed by the tension of the dermis over thepoints of the skeleton, as mentioned above), and branch and anastomoseon the membranes. Under the microscope they are seen not tobe special fibre-structures, but to consist simply of thickened membrane.The membrane is coloured by purplish cells, which are about•03 millim. in diameter, and are crowded with scmiopaque granules,to which they owe their colour. The fibres of the skeleton have awide central cavity, occupying about half their diameter, and filled,or almost so, witli a transparent substance coloured diftusely of apurplish-red colour. The walls of the fibre are composed of laminaewhich separate readily, and may then be seen to consist of a darkBubstance, rather readily torn, thickly set with fine dark purple-red