390 



THE MICROSCOPE. 



found in it gemn.ules still retaining their brown coloul 

 and contents capable of development. 



Pig. 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, intermarninal cavities ; 6, the basal diaphragms ol 

 the intermarginal cavities : c, imbedded ovaria forming the dermal crust ol 

 the sponge ; d, the large patentoternate 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 Spotyjiadce, Ray Soc. p. 10P. 



