BPONOIIDA. 3!>1 



APLTSINID^E. 



Aplysinida, Carter, Ann. ,y Mag. N. II. (6) ivi. 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, FJi-nch. Zoupk. p. 398. 



Spongia membranacea, Esper, Pflanzenth. ii. p. 256, pi. xxxiv. 



planthella concentrica, Hyatt, Mem. Bost. Soo. ii. p. 407. 



? Aplysina purpurea. Carter. Ann. ty Mag. X. II. (6) vi. p. 36. 



A very fine species, fortunately preserved in spirit as well as in the 

 dry state. It forms a cylindrical mass, which has the same general 

 form as that given in Esper'a figure (I. c); the base of the wet 

 specimen is about 40 millim. (1-jj-itich) in diameter. The dry speci- 

 men, which is much the largest of the two, is 5si i millim. ( 22.] inches) 

 high, and the maximum diameter, which is at about 5 inches above 

 the base, is about 40 millim. (1^ inch). At 77 millim. (3 inches) 

 above the base a branch is given off, 22 millim. (§ inch) in maximum 

 diameter and 145 millim. (9| inches) in length, and on the same 

 side, 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 in- 

 terior of the cylindrical column of which the sponge consists. They 

 throw out branches somewhat freely from their sides, and subdivide 

 terminally into ramifying branches; the resulting twigs anastomose 

 freely, the superficial ones end in outwardly and upwardly directed 

 points, usually hi- or tri-furcate, which are just covered by the 

 tough dermis; the apices are -18 to -28 millim. in diameter. The 

 dermis and the internal membranes consist of a tough membrane 

 of 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 nume- 

 rous raised thickened lines, which radiate from the projecting apices 

 of the dermal conuli (formed by the tension of the dermis over the 

 points of the skeleton, as mentioned above), and branch and anasto- 

 mose on the membranes. Under the microscope they are seen not to 

 be special fibre-structures, but to consist simply of thickened mem- 

 brane. The membrane is coloured by purplish cells, which are about 

 •03 millim. in diameter, and are crowded with semiopaque granules, 

 to which they owe their colour. The fibres of the skeleton have a 

 wide central cavity, occupying about half their diameter, and filled, 

 or almost so, with a transparent substance coloured diffusely of a 

 purplish-red colour. The walls of the fibre are composed of laminae 

 which separate readily, and may then be seen to consist of a dark 

 substance, rather readily torn, thickly set with fine dark purple-red 



