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EXPLANATION OF THE PLATES. 



S. 1., S. j, Ac., indicate which of Swift's objectives were used in making 



the drawings. 



PLATES A, B, and C illustrate the structure and life-history of typical 

 Simple and Compound Ascidians. (See Introduction, p. xiv. , ct scq.) 



PLATE A. 



Fig. 1. An Ascidia, from the right-hand side, nat. size. 



Fig. 2. Diagrammatic transverse section through the atrial aperture, 



along line A B in fig. 4. 



Fig. 3. Part of wall of hranchial sac, magnified. 

 Fig. 4. Diagrammatic longitudinal section along the line A B in 



fig. 2. 



Fig. 5. Diagram to show structure of mantle and test (body-wall). 

 Fig. 6. Diagram to show the relations of nerve ganglion, neural gland, 



duct, and dorsal tubercle. 

 Fig. 7. Front of dorsal edge of branchial sac, showing tentacles, dorsal 



tubercle, languets, Ac., magnified. 



PLATE B. 



Fig. 1. Colony of Colclla Quoyi (Distomidae). 

 Fig. 2. Colony of Leptoclinum najlcctnin- (Didcmnida, 1 ). 

 Fig. 3. Colony of Pharyngodictyon ininibilc (Polyclinidu. 1 ,). 

 Fig. 4. Colony of Botryllus Scldoxsei / (Botryllidte). 



(All nat. size, after Herdman, " Chall." Keport). 

 Fig. 5. Diagrammatic section of a Compound Ascidian colony, showing 



parts of two Ascidiozooids and a common cloacal aperture, 



magnified. 



Fig. 6. Ascidiozooid from a Botryllid colony. 

 Fig. 7. Ascidiozooid from a Distomid colony. 

 Fig. 8. Ascidiozooid from a Polyclinid colony. 



(All from right side, magnified). 



