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SHELL GALLERY. 



lid is open. The Mediterranean species R. callense (Fig. 13) grows 

 attached to the rocks. The little exhibited specimen is on a fragment 



Fig. 13. 



Bhodosoma callense, X 10. A, " valve " open ; B, shut. 

 a, branchial ; b, atrial orifice. (After Lacaze Duthiers.) 



of shell in front of a black patch. The figure shows specimens with 

 the lid open and closed. 



Family Clavelimdce. The body is attached to a creeping 

 stolon or mass of stolons, from which new individuals arise by 

 budding. The other three families of Simple Ascidians included 

 solitary forms, but the Clavelinidge are social, and form colonies 

 wherein each individual has its own test. 



Glavelina lepadiformis (Fig. 14) forms graceful crystal vases about 

 an inch in height. The figure shows one individual, but usually 

 the processes at the base extend out as stolons whence other 

 individuals arise. 



Diazona violacea, from Cornwall, forms beautiful purple disk- 

 shaped colonies in which the ascidiozooids arise from a basal mass 

 of stolons. Sometimes the ascidiozooids die down, leaving only a 

 smooth violet pad, which in due time produces a new crop of ascidio- 

 zooids. 



