TUNICATA. 



253 



emits, at night, a most brilliant phosphorescent light, 

 whence the derivation of the name by which it is 

 distinguished. Nothing can exceed the dazzling 

 splendour and brilliant colours exhibited by these 

 floating cylinders colours passing rapidly from a 

 dazzling red to saffron, to orange, to green, and to 



FlG. 191. PYROSOMA. 



azure, and thus reflecting every ray into which the 

 prism divides the light, or which is exhibited by the 

 heavenly bow. 



If when walking on the sea-shore, about low- water 

 mark, we turn over large stones, or look under pro- 

 jecting eaves of rock, we are almost sure to see 

 translucent, jelly-like masses of various hues of orange, 

 purple, yellow, blue, grey, and green, sometimes 

 nearly uniform in tint, sometimes beautifully varie- 

 gated, and very frequently pencilled as if with stars 

 of gorgeous device, now encrusting the surface of 

 the rock, now depending from it in icicle-like pro- 

 jections. These are 



Compound Ascidians. A tangle or broad-leaved fucus 

 torn from its rocky bed, or gathered on the sands, 

 where the waves have cast it, will show us similar 

 bodies, mostly star-figured, investing its stalks, wind- 

 ing amongst its roots, or clothing with a glairy coat 

 the expanse of its foliated extremities. If we keep 

 some of these in a vessel of sea water, we find they 

 lie as apathetic as sponges, giving few symptoms 



