Ascidians. 21 



compound xA.scidians, which form a common mass and reproduce 

 by gemmation or budding. 



Such compound Ascidians are found in abundance on rocks 

 and stones uncovered b^' the tides, forming gelatinous expansions 

 wliich attract tlie eye by their brilliant colours, Bo/ryllus 

 violaceus appearing as a beautiful mass of purple, on which 

 groups of individuals stand out as tiny greenish-white stars. 



Tliis Botfvlliis, common on all our rocky coasts, is an 

 excellent example of a compound Ascidian, not a single animal, 

 but a commonwealth of beings combined into sj'stems, systems 

 combined into masses. It is not surprising that such creatures 

 have long been regarded as Polyps, and, no doubt, they bear 

 some resemblance to certain representatives of the Coral tribe. 

 Each star in the colonv of Botrylhts, as represented in the figure 

 on page 20, constitutes a sj'stem with as many components, each 

 having its own mouth, as there are branches to the star, while 

 a common vent is present in the centre. Another compound 

 Ascidian, found locally on our coasts, is the Sea-fig {Polyclinum 

 ficus), sometimes forming vast masses of olive-green colour, 

 in the interior of which the viscera of the individuals appear as 

 yellow spots suggestive of the seeds of a fig. 



