TUNICATES OR ASCIDIANS AND LANCELETS 117 



An allied Ascidian, Ascidiella, is abundant on muddy 

 bottoms, where it forms large masses suggesting plant 

 tubers. Another group forms huge leathery patches 

 and are of a vivid colour. One such, Leptoclinum, is 

 abundant in certain caves in the Channel Islands, and 

 Victor Hugo in his " Toilers of the Sea " refers to it in the 

 passage, " the walls are splashed with crimson stain as if 

 giants had been fighting there." 



A number of common and beautiful species are included 

 in the genus Botryllus, one — Golden Stars — often covering 

 stones and weed plants with richly tinted shapeless masses, 

 made dazzling by a pattern of golden stars that stand out 

 in vivid relief against a background of reddish brown 

 or deep jade green. Botryllus is one of the very numerous 

 " compound " Ascidians, in which the individuals are 

 joined one to the other, forming masses of varying form 

 and extent. 



Yet another group of Tunicates leads a free floating 

 life in the open sea, one of the commonest being the trans- 

 lucent Salpa. This demonstrates " alternation of genera- 

 tions." A solitary Salpa being hatched from an egg pro- 

 duces a chain of buds often breeding hundreds and reaching 

 a considerable length. The buds in turn set free groups, 

 each bud containing one egg, and so the series — chain 

 Salpa, solitary Salpa, chain Salpa, and so on — goes on 

 indefinitely. 



A remarkable species of Ascidian, Oikppleura — the 

 Housebuilder — retains the larval tail throughout life, 

 swimming powerfully and continually investing itself with, 

 and discarding, a large gelatinous structure many times 

 its own size and entirely covering the body. 



