PORIFERA. 



65 



a remarkable class of organized beings, dubi- 

 ously admissible into the animal series, usu- 

 ally known by the name of Sponges, which 

 are met with in great abundance in the seas 

 of most climates, either growing in isolated 

 masses from the rocks or spreading out so as 

 to encrust the surfaces of submarine bodies 

 with a kind of living carpet, the texture of 

 which varies in accordance with the nature 

 of the sponge. By recent naturalists, the 

 term AMORPHOZOA (a/n6p<t>os, shapeless; woi', 

 animal) has been considered a preferable de- 

 signation, and accordingly these names will 

 be applied indiscriminately throughout the 

 present article. 



According to the most recent authors, the 

 members of the class before us may be se- 

 nerally described as follows : " Organized 

 bodies growing in a variety of forms, perma- 

 nently rooted, unmoving and unirritable, 

 fleshy, fibro-reticular or irregularly cellular, 

 elastic and bibulous, composed of a fibro- 

 corneous axis or skeleton, often interwoven 

 with siliceous or calcareous spicula, and con- 

 taining an organic gelatine in the interstices 

 and interior canals ; reproduction by gelati- 

 nous granules generated in the interior, but 

 in no special organ. All are aquatic, and, 

 with a few exceptions, marine." * 



The families composing the class thus cha- 

 racterised are distinguished by the nature of 

 the skeleton or solid framework upon which 

 their shape depends, in accordance with which 

 Blainville has arranged them as follows : 



ALCYONCELLUM. Body fixed, soft, sub- 

 gelatinous, solidified by tricuspid spicula, 

 phytoid ; branches not numerous, cylindrical, 

 fistular, terminated by a rounded orifice, with 

 thick walls composed of regular granules ; 

 polygonal, alveoliform, pierced with a pore 

 externally and internally. 



SPONGIA. Body soft, very elastic, multi- 

 form ; more or less irregular, very porous, 

 traversed by tortuous canals, which are nu- 

 merous, opening externally by distinct oscula, 

 and formed by a kind of subcorneous sub- 

 stance which anastomoses in every direction ; 

 entirely without spicula. 



CALCISPONGIA. Body not very soft,formed 

 in irregular masses, porous, trave'rsed by irre- 

 gular canals, which open externally by oscula, 

 and composed of a subcartilaginous substance, 

 supported by calcareous spicula that are, for 

 the most part, stelliform. 



HALISPONGIA (xaAis, silcx). Body more 

 or less rigid or friable, in an irregular mass, 

 porous, traversed by tortuous canals termi- 

 nating by oscula scattered over the whole sur- 

 face, and composed of a subcartilaginous sub- 

 stance supported by simple spicula, which 

 are silicious. 



SPONGILLA. Body an irregular mass, more 

 or less rigid and friable, pierced with pores, 

 but without true oscules, composed of a fibro- 

 cartilaginous substance, which is in small 



* History of British Sponges and Lithopfaytes, by , Tetliea Cranium of the natural size ; b, section 

 George Johnston, M. D., Edinburgh, 1842. ' of the same. (After Johnston.) 



VOL. IV. F 



quantity compared with the great number of 

 simple silicious spicula which solidify it. 



GEODIA. A fleshy body, tuberiform, irre- 

 gular, hollow internally, and formed externally 

 by a sort of crust or envelope pierced with a 

 great number of pores, and containing a group 

 of oscules or larger pores placed in a little 

 subcircular space. 



SIPHONIA. Body polymorphous, free or 

 fixed, composed of dense fibres, forming two 

 sorts of canals, some larger and longitudinal, 

 opening by oscula at the bottom as well as 

 on the summit, the others transverse and 

 anastomosing, radiating towards the periphery, 

 and provided with a terminal depression, more 

 or less considerable, in which the oscules are 

 collected in a radiated manner. 



SCYPHIA. Body cylindrical, simple or 

 branched, terminated by a large rounded os- 

 cule, and entirely composed of reticulated 

 tissue. 



EUDEA. Body filiform, attenuated sub- 

 pedunculate at one extremity, large, round, 

 and pierced with a great oscule at the other, 

 with pores scarcely visible in irregular lacuna? ; 

 whole surface reticulated. 



HALLIRRHOA. Body turbinated ; almost 

 regular, with the circumference circular or 

 lobed, covered with cellules or pores, which 

 are indistinct externally, with a large oscule 

 in the centre of its enlarged part. 



TETHIUM. Body subglobular, irregular, 

 tuberiform, sarcoid but firm, suberous, re- 

 sisting, supported by and mixed up with an 

 immense quantity of aciculi, which are simple, 



Fig. 67. 



