6 Mr. J. Hogg on the Horny Sponges. 



reous Sponges. — Fibres of a somewhat cartilaginous substance, 

 with the spicula calcareous, or consisting of carbonate of lime. 

 Examples : S. compressa, S. botryoides, &c. 



Division IV. S. Subcartilagineo-silicea . The Subcartilagino-siliceous 

 Sponges. — Fibres composed of a somewhat cartilaginous sub- 

 stance, with siliceous spicula. 

 Examples : S. tomentosa, S. palmata, and Spongilla fluviatilis. 



Division V. S. Subereo-silicece. The Subereo- siliceous Sponges. — 

 Fibres of a corky substance, with long siliceous spicula. 

 Examples: S. verrucosa (Mont.) and S.pilosa (Mont.). 



At present, as far as I am aware, no sponges have been dis- 

 covered either Avith horny fibres and calcareous spicula, or 

 with corky fibres and calcareous spicula. The other parts of 

 the sponges, such as the membrane and gelatinous portion, are 

 of too fugacious a nature to afford any useful characters for 

 the arranging of the Order ; the skeleton itself, consisting of 

 fibres as well as spicula (which exist in so many sponges), 

 clearly offers the best characters for that purpose. The pre- 

 ceding divisions I did in part derive from M. Milne Edwards's 

 observations in his edition of M. de Lamarck's * Hist. Nat. des 

 Anim. s. Vert.,' torn. ii. pp. 535 — 541. And, inasmuch as no 

 better arrangement of the Spo^igiee has yet appeared, I am in- 

 duced to think the preceding attempt may prove of use, and 

 assist the observer in rendering perfect a general classification 

 of them. But this cannot be effectually accomplished until 

 further investigations shall have been made on the Sea Sponges 

 in their natural state ; and for the purpose of urging those 

 who have the opportunity to do so, 1 will here repeat the re- 

 marks which I have before made in a note at p. 406, vol. xviii. 

 of the * Linn. Trans.' : — " The difficulty of preserving sponges, 

 even in bottles filled with rectified spirit of wine, is so great, 

 that no one who has not the means of examining them in a 

 fresh condition and in their native element, can ever expect 

 to throw much light on their variously-formed" structures. 

 The dried masses of fibrous skeletons, devoid of their true 

 natural forms and colours, w-ithout their parenchymatous jelly 

 and enveloping membrane, &c. as exhibited in our museums, 

 can but little assist us in obtaining a correct knowledge of 

 their natural history." 



I remain. Gentlemen, yours truly, 



John Hogg. 



London, May 1st, 1811. 



