106 CEYLON PEARL OYSTER REPORT. 



Fig. 61. The same seen from the ventral aspect while crawling over a glass plate. The dotted outlines 

 a and b show the leech-like mobility of the anterior region of the body in attitudes assumed 

 frequently when the worm is restless, f.f., tube feet. The other letters as in fig. 60. 

 62. View of the posterior extremity of the same, from above, showing the sucker-pits (s.p.) closed 

 by the approximation of their lips. The fine transverse wrinkling characteristic of the dorsum 

 of the trunk is also shown in the figure. 

 63. Ciliated ectoparasite from gills of pearl oyster with paired trilobed eyes. 



61. Another characteristic appearance of the same. A contractile vacuole is seen posteriorly and two 

 triradiate eye-spots anteriorly. 



65. Diagram of pearl oyster to show at a the position of the cyst enclosing MvsaUa hcrdmani, in the 

 tissues of the pearl oyster. x . 



66. A portion of the pedal disc seen when an Aspidogasier margaritiferce is detached from its hold and 

 turned upon its back. The edges of the disc then recurve inwards to varying degrees. 



67. Highly magnified view of the end of a proboscis of Tetrwrhynchus minimus, showing the various 

 sized hooks and their arrangement. 



68. Tube feet of Aspidogaster margaritiferce in various states of extension and retraction. 



69. a, b, c, successive attitudes assumed by .-/. margaritiferce during progression, d, another view of 

 the same when about to change position. 



70. Head of Tetrwrhynchus minimus. 



71. Optical section of the same. 



72. Tetrarhynchus minimus, showing proglottides. 



Note. Owing to an error in the lithographer's office, Plates III. and IV. have been 



printed as 3 and 4, in Arabic numerals. 



