I )itroducfwii to Animal Morphology. 77 



sandy axis, while others are fine, homogeneous (Hircinia). 

 Auliskia has its fibres traversed by an Algoid ? Cacospongia 

 is loose in texture, with laminated, slightly elastic threads. 

 Spongelia is hard, brittle, and scarcely elastic. 



Order 3. Gumminae — horny, caoutchouc-like Sponges 

 composed of densely interwoven homogeneous or striated 

 fibres, or of mucous tissue imbedding stellate spicules. In 

 the basis are often cartilage-like cells {Kolliker). Spicules 

 may be candelabriform (Corticium), or none (Gummina), or 

 there may be an outer surface of compacted fibres and stellate 

 spicules (Chondrilla). 



Order 4. Halichondriae — siliceousSponges, with no cortical 

 layer, and a small amount of Spongiolin, with no anchorate 

 nor defensive spicules. They may be massive, with cylindrical 

 needle-like spicules (Halichondriidse) ; or rugose, with simple 

 spicules usually pointed at both ends (Reniera) ; or blunt, 

 often knobbed at the end (Suberites). Ancorina is fleshy, 

 with acicular spicules. Clionidas are mostly boring Sponges, 

 with pin-shaped spicules, perforating oyster-shells, limestone,. 

 &c. They have often two kinds of papillje, pore-bearing, 

 small, and osculum-bearing, larger, fewer. The surface may 

 be beset with siliceous polygonal plates (Cliona), or mulberry- 

 like bodies (Thoosa). Raphiophora patera (Neptune's cup) 

 is a large goblet-like Sponge, 2-4 feet in height, with 

 numerous octoradiate oscula. Raphyrus is an allied, irregular 

 form. The family Arenospongidse, including the genus 

 Xenospongia, which forms a disc of agglutinated sand, and 

 possesses diverging spicules in the sarcode and around the 

 oscula, may be worthy of ordinal rank. 



Order 5. Corticatae — globose, tuberous or branched, with 

 an outer cortex containing spiculigerous corpuscles, and an 

 inner layer of Spongiolin threads and siliceous needles, often 

 in radiating sheaves. Sometimes the cortex is thin, mem- 

 branous (Tisiphonia), or thicker, provided with siliceous, 

 globules and needles (Geodia), or globules only (Caminus). 

 Pachymatisma has short fascicles of spicules, and an unsym- 

 metrical central mass. Tethya is massive, sub-orbicular, with 

 a skeleton of fasciculate spicules radiating to the surface, with 

 sub-cuticular unsymmetrical cavities. The cortical spicules- 



