JOURNAL OF MICROSCOPICAL SCIENCE. 



DESCRIPTION OF PLATE XVIII, 



Illustrating Mr. C. Stewart's paper on a New Sponge, 

 Tethyopsis cnlumnifer. 



Fig. 

 1. — The sponge of the natural size. 



2. — Ditto, with the basal portion and lower part of the stem in section. 

 3. — Under surface. 

 4.— Spiculum of the lower portion. 

 5. — Spiculum of the axis of the stem. 

 6. — Stellate spicula of the dermal membrane. 

 7. — Stellate spicula of the sarcode. 



