390 



THE MICROSCOPE. 



found in it gemmules still retaining their brown colour 

 and contents capable of development. 



Fig. 214. Geodia Barretti (Bowerbank). 



A. section at right angles to the surface, exhibiting the radial disposition of the 

 fasciculi of the skeleton, and a portion of the dermal crust of the sponge, 

 magnified 50 diameters, a, interrnarginal cavities ; b, the basal diaphragms of 

 the intermarginal cavities ; c, imbedded ovaria forming the dermal crust of 

 the sponge ; d, the large p'atentoternate spicula, the heads of which form the 

 areas, for the valvular bases of the intermarginal cavities ; e, recurvo-ternate 

 defensive and aggressive spicuia within the summits of the intercellular 

 spaces of the sponge ; /, portions of the interstitial membranes of the 

 sponge, crowded with minute stellate spicula ; g, portions of the secondary 

 system of external defensive spicula. (1) 



The usual contents of the gemmules have been described 

 by Meyen (Muller's Archiv. 1839, p. 83). In many in- 



(1) See Bowerbank's Monograph of the British Spougiadcc, Ray Soc. p. 169. 



