PYROSOMA. 



brilliant colours exhibited by these floating cylinders colours passing rapidly 

 from a dazzling red to saffron, to orange, to green, and to azure, anof thus re- 

 flecting every ray into which the prism divides the light, or which is exhibited 

 by the heavenly bo\v. 



FIG. 191. PYROSOMA. 



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

 turn over large stones, or look under projecting 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 variegated, and very fre- 

 quently pencilled as if with stars of gorgeous device now encrust- 

 ing the surface of the rock, now depending from it in icicle-like 

 projections. 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, winding 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 

 of vitality. A closer and micro- 

 scopic inspection, however, will 

 soon show us currents in the water 

 surrounding them, streams eject- 

 ed from their apertures, and water 

 rushing in, indicating that, how- 

 ever torpid the creature may ap- 

 pear externally, all the machinery 

 of life, the respiratory wheels and 

 circulatory pumps, are hard at 

 work in its numerous recesses. The 

 whole mass, in fact, is composed 

 of an aggregation of minute Ascidians, conjoined in elegant microscopic 



FIG. 192. Co.MPOL-NDAsciDiAX. STARRY BOTRYLLUS.* 

 a, natural size ; b, one of the composite stars magnified. 



* fiarpvs, botrys, a bunch of grapes. 



