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TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



shape and the 2 apertures. There are many interesting 

 and some puzzling points in connection with the structure 

 and mode of life of Ascidia, but these would require many 

 figures and a microscopic examination of the animal for 

 their exposition. Another simple Ascidian which we fre- 

 quently have in the Aquarium is Styelojisis grossularia (2), 

 " the red-currant squirter of the sugar-loaf rock," as it has 

 been called, because of the myriads which cover with a 

 red papillated surface many square yards of the cliff in 

 the beautiful caves near Spanish Head. 



Compound Ascidians are colonies each member of 



Fig. XXI. 



which is very much like a simple Ascidian in structure, 

 but they are all united together by one covering or tunic. 

 A common and very brightly coloured kind of Compound 

 Ascidian is BotrylJus, shown at 5 in fig. XXI., and com- 

 monly found under stones about low-water mark. The 

 colony is marked with bright stars and wheels, each ray of 

 which is a separate member of the colony, with complete 

 organisation of its own. There are many other kinds of 

 Compound Ascidians (such as that shown at 4) ; they rival 

 the sponges in their curious shapes and brilliant colours. 



