THE PAEASITES OF THE PEABL OYSTER. 105 



Fig. 36. A single tooth of T. pinna: 

 ,, 37. A portion of the introverts of T. pinnce, showing the oblique rows with enormous numbers of 



weak teeth. 

 38. A section through the head, cut in two places, and showing the four proboseides and the bladder, 



with widely separated walls, of T. pinna;, magnified to the same extent as figs. 39 and 40. 

 ., 39. A section through the head, cut twice, and the bladder of T. balistidis showing the four 



introverts, magnified to the same extent as fig. 38. 

 40. A section through the same, showing the junction of the head with the inner wall of the 



bladder. 



PLATE III. (3 on Plate). 



Head end of Cheiracanthus wncinahis. gl., glands; int., intestine; /., lip; ce., oesophagus. 



Tail end of Ascaris meleagrince. ".;//., anal glands ; int., intestine. 



Head of Ascaris meleagrince, seen from above. 



Head end of Cheiraca/nthus imcinatus, inflated, x 30. 



The same collapsed. 



The whole worm, Cheiracanthus imcinatus. x 6. 



Diagrams showing usual position of Cheiracanthus imcinatus within the adductor muscle. Natural 



size. 

 Posterior extremity of Cheiracanthus uncinatus. x 30. 



Ventrolateral view of Aspidogaster margaritifera. In this specimen the tube feet were all 

 retracted. The natural size is shown by the small figure on the right. 

 50. Side view of the same with extended tube feet. The natural size is shown by the small figure 



on the right. 

 51. Views of spirit specimens of Musalia herdmani, magnified. 



52. Transverse section through the suckers and tube feet of A. margariiiferce, highly magnified. 

 53. Cercaria of Mvttua margaritifera within its cyst capsule. Extracted from the branchial tissue of 



a pearl oyster. x 30. 

 54. The same under greater magnification, x 10. Lettering as in fig. 55. 



,, 55. The same larva freed from its capsule, and under slight pressure. x 90. c.s., cuticular spines ; 

 c.v., excretory vesicle; d.?., digestive caeca; c, eye-spots; e.v.p., excretory pore; p.sli., penis 

 sheath; ph., pharynx; s.v., seminal vesicle ; v.s., ventral sucker. 

 ,, 56. Penis sheath of same larva. 



,, 57. Anterior extremity of same larva. x 240. c.s., cuticular spines; e., eye; cz.t., excretory 

 tubules. 



PLATE IV. (4 on Plate). 



Fig. 5S. Musalia herdmani, immature specimen from the mantle of a pearl oyster. Natural appearance 



fully extended. Letters as in fig. 59. 

 ,, 59. The same shortened and broadened under pressure. Life size on right, c.v., excretory vesicle ; 



i(.'\, digestive cseca; ex.p., excretory pore; ex.t., excretory trunks; (B.p., oesophageal pouch; 



o.s., oral sucker; or., ovary ; ph., pharynx; p.sh., penis sheath; t., testis; v., vagina; v.s., ventral 



sucker. 

 ,, 60. Aspidogaster margariiiferce; adult from the pericardial chamber of a pearl oyster, seen ventro- 



laterally. The tube feet are retracted. dig.C, digestive caecum ; rx.t., double excretory trunks; 



o.s., oral sucker; p.d., pedal disc ; ph., pharynx; s.p., sucker pits. 



P 



