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TUNICATA. 



The Tunicata are marine animals, the majority of which live, in Wall Case 

 their adult stage, a stationary life, fixed to the rocks or sea-bottom, 

 but a comparatively small number are free-swimming. 



They occur in the form of cartilaginous or leathery sacs, fleshy in- 

 crustations, solid fleshy masses, free-swimming, barrel-shaped animals, 

 solitary or united into chains or hollow cylinders ; or, lastly, of minute 



Fig. 1. 



to left 

 of maiu 

 entrance 

 to Shell 

 Grallery. 



yv 



at 



V, 



;^ 



Ascidia mentula from the right side. 

 at, atrial aperture ; hr, branchial a^Derture ; t, test. 

 [After Herdman : Tunicata, Encj^c. Britannica.] 



free-swimming tadpole-shaped organisms. To explain briefly the 

 structure of a Tunicate, Ascidia mentula (Fig. 1), is selected. The 



G 2 



