agS TADPOLES OF THE SEA 



of colours contrasting with that of the sheet-Uke 

 tUiTiic in which they are embedded, so that the sheet- 

 like growth looks like a piece of woven fabric with 

 ,a radiated star pattern repeated all over its surface. 

 Purple and green, yellow and orange in various shades 

 are the colours contrasted in the stars and groundwork. 

 ,This extraordinary arrangement of little animals as 

 flattened sacs grouped like the rays of a star 4n a gela? 

 .tinous bed or matrix is as unlike avertebrate fish ort^d- 

 pole as anything can be ; yet the animals composing this 

 star-spangled jewel actually lay eggs, from each- of which 

 a tadpole hatches ! The. Botryllus, as this beautiful 

 enci;ustation is called, is one of those exceptional Ascidians 

 .which have retained the tadpole phase, or young form (often 

 called a "larva," the name applied to the. caterpillar of 

 .^oths and butterflies), in their growth fronj the egg> The 

 Botryllus tadpole, after some days of a free-swimm.ing 

 Jife, fixes itself by its head to a solid stone or weed, and 

 .changes into a starrshaped group, from which, other gout 

 nected star-groups are- budded ofi", whilst remaining 

 embedded in a common gelatinous sheet exuded by 

 themj and holding them together !- 



Though we can often prove that the brilliant colouring 

 and pattern-marks of an animal or a plant are of advanr 

 tage to their possessor, either as attracting other animal? 

 to it or as concealing it frpm enemies or warning others 

 to leave it alone, yet there is a vast preponderance of 

 cases in which we cannpt ascribe any special " use " to 

 the. colour, as colour. • It happens that certain chemical 

 bodies necessarily manufactured by the plant or animal in 

 the course of its living changes are of this or that colourj 



jpst as water is blue and iron^rust is red, and so there 



the brilliant colour is. ~ ^"4 so far as the advantagaof 

 the animal or plant, is concerned, it might just as well not 

 bC; there at all ! Jhis yselessn ess of beautiful colpuring 



