138 Dr Grant's Observations on the Structure 



the existing species have yet been brought to light from their 

 recesses in the depths of the ocean. This animal still alFords 

 many curious and interesting subjects of inquiry to those who 

 have leisure and opportunities of examining the more perfect 

 species of tropical seas ; and, though probably the simplest of 

 animal organisations, the investigation of its living habits, its 

 structure and vital phenomena, and the distinguishing charac- 

 ters of its innumerable polymorphous species, is peculiarly cal- 

 culated to illuminate the most obscure part of zoology, to exer- 

 cise and invigorate our intellectual and physical powers, and to 

 gratify the mind with the discovery of new scenes of infinite 

 wisdom in the economy of Nature. 



PLATE II. 



Fig. 1. Silicious, double-pointed, curved spiculum of the Spoil' 

 gilla friahilis. (See Edin. Phil. Jour. vol. xiv. p. 279.) 

 This and the following 19 figures are magnified 50 times. 



Fig. 2. Silicious, fusiform, curved spiculum of the Spongia pa- 

 pillaris. (See Edin. New Phil. Jour, vol, i. p. 346). This 

 spiculum occurs in Spongia tomentosa, or urens, S. crislata, 

 and large in S. coalita. 



Fig. 3. Silicious, double-pointed, curved, short spiculum of the 

 Spongia cinerea, Gr. (See zoological notices at the end of 

 the present Number.) This spiculum occurs half as large in S. 

 oculala, S. palmata, S. dichotoma, S. prolifera, and S. cancel- 

 lata, Sowerby. 



Fig. 4. SiHcious, single-pointed, straight spiculum of the Spon- 

 gia panicea. (See Edin. New Phil. Jour. vol. i. p. 347-) 

 This spiculum occurs slightly curved in the S. parasitica, 

 Mont. 



Fig. 5. Silicious, long, waved filament, obtuse at both ends, of 

 the Spongia ventilabrum (see Edin. New Phil. Jour. vol. i. 

 p. 349.), occurs along with another silicious spiculum, similar 

 to fig. 18. 



Fig. 6. Silicious, single-pointed, curved, thick spiculum, with a 

 round head on its obtuse end, of the Spongia patera. (See 

 Edin. New Phil. Jour. vol. i. p. 348.) 



Fig. 7- Silicious, single-pointed, curved, slender spiculum, with 

 a round head on its obtuse end, of the Cliona celata. (See 

 Edin. New Phil. Jour. vol. i. p. 80.) 



