10 A MONOGRAPH OF THE 



4. Spongilla, Linnaus, Lamarck, and Johnston. 



Skeleton without fibre, composed of a symmetrical network 

 of spicula ; the primary lines of the skeleton passing 

 from the base or centre to the surface, and the 

 secondary lines disposed at about right angles to the 

 primary ones. Reproductive organs, ovaries, coria- 

 ceous and abundantly spiculous. Vol. I, p. 199. 



All the species are inhabitants of fresh water. The best 

 type of the genus is Spongilla Jluviatilis, Johnston. For 

 the structural form of the skeleton, see skeleton of Isodidya 

 Normani. Vol. I, Plate XXXVI, Fig. 376; and for the 

 ovaries, Plate XXII, Pigs. 317, 318, 319, 320, 321, and 

 Plate XXIII, Figs. 322, 323. 



Suborder IV. Spiculo-fibrous skeletons. Regularly fibrous. 

 Fibres filled with spicula. 



1. Desmacidon, Bowerbank. 



2. Raphyrus, Bowerbank. 



1. Desmacidon, Bowerbank. 



Skeleton fibrous, irregularly reticulated. Fibres composed 

 entirely of spicula arranged in accordance with the 

 axis of the fibre, cemented together and thinly coated 

 with keratode. Vol. I, p. 200. 



Type, Desmacidon fruticosa, Bowerbank. Vol. I, Plate 

 XIII, Fig. 264. 



2. Raphyrus, Bowerbank. 



Skeleton fibrous, but not horny. Fibre composed of a 

 dense mass of siliceous spicula mixed together with- 

 out order. Vol. I, p. 201. 



