SYNAPTA VIVIPARA. 87 



Fig. 37. Longitudinal section of a part of genital duct, to show its structure and position in the mesentery. I, lumen of 

 duct; g. e., germinal epithelium; m. e., epithelium of mesentery. 950x. 



Fig. 38. Transverse section of dorsal body-wall of an adult, to show the termination of the genital duct, sp, sper- 

 matozoa. 225x. 



Fig. 39. Longitudinal section of a small part of genital gland, to show the position of ovum, pressing against the epi- 

 thelium of the gland, epi, epithelium of gland ; ov, ovum. 500x. 



Fig. 40. Transverse section of genital gland, to show its structure and the position of the ova (ov). 500x. 



PLATE 13. 



Fig. 41. Transverse section of the ectoderm of a pentactula, to show the invagination whiclrforms the larval glandular 

 organ. 500x. 



Fig. 42. Transverse section of the same organ, fully grown, from the body-wall of a ten-tentacled larva. 500x. 



Fig. 43. Longitudinal section of one of these organs, to show the peripheral position of the nuclei, and the lumen at the 

 center. 600x. 



Fig. 44. Interradial plate from the calcareous ring of an adult. 35x. 



Fig. 45. Radial plate from the same ring. 35x. 



Fig. 46. The development of these calcareous plates, a, youngest stage ; b-g, successively older stages ; n, older stage 

 of an interradial plate ; i, older stage of a radial plate. 225x. 



Fig. 47. Part of the calcareous ring of an old ten-tentacled larva, to show the growth of the radial plate (r.p.) of the 

 calcareous ring, in support of the developing eleventh tentacle, ip, interradial plates. 65x. 



Fig. 48. Calcareous rods from the tentacles of a ten-tentacled larva. 225x. 



Fig. 49. Calcareous rods from around madrepore. 225x. 



Fig. 50. Miliary granules from the skin of an adult. 225x. 



Fig. 61. Anchor from the skin of an adult. 120x. 



Fig. 52. Normal anchor-plate from an adult. 120x. 



Fig. 53. Abnormal anchor-plate from an adult. 120x. 



Fig. 54. Longitudinal section of the tentacle of an old pentactula, to show the thickened ectoderm at the tip. 225x. 



Fig. 55. Cross-section of a young tentacle, to show the entire separation of the canals of the digits from the central 

 canal of the tentacle. 225x. 



Fig. 56. Longitudinal section of part of a young tentacle, to show the origin of the digits, as outgrowths of the tentacle- 

 canal. 226x. 



Fig. 57. Tentacle of an adult. 22x. 



Fig. 58. Transverse section of a mesentery and intestine of a pentactula, to show the origin of the haemal system from 

 the right lamina of the mesentery. 500x. 



Fig. 69. Loop of intestine in a small adult, to show formation of the transverse vessels of the haemal system. 35x. 



Fig. 60. The same from an older specimen. 65x. 



Fig. 61. Cross-section of the dorsal mesentery of a larva one mm. long, to show the beginning of the ciliated funnels. 

 575x. 



Fig. 62. The development of the ciliated funnels, a, the first large cells seen from above looking down on the surface 

 of mesentery ; 6, increased number of cells ; c, slightly older stage seen from the side ; d, older stage, surface view ; e, older 

 stage, seen partly from the side ; /, older stage seen from the side. 575x.. 



Fig. 63. Longitudinal section of a funnel, to show its structure. 950x. 



Fig. 64. Ciliated funnel of an adult, seen from in front. 575x. 



Fig. 65. Ciliated funnel of an adult, seen from above. 225x. 



Fig. 66. Surface view of stone-canal of an adult, to show its course from water-ring to the exterior. 35x. 



PLATE 14. 



Fig. 67. Cross-section of stone-canal and genital duct of an adult before they enter the body-wall. 225x. 



Fig. 68. Cross-section of stone-canal and genital duct of same adult in the body-wall. 225x. 



Fig. 69. Cross-section of same stone-canal as it approaches the body-wall. 225x. 



Fig. 70. Cross-section of the same, where it opens to the exterior. 225x. 



