TWO PAKASITIC FOKMS OF THE FAMILY TETRAEHYNCniDiE. 341 



Fig. 7. Magn. 350 diam. Inorganic nodules " calcai-eous particles : " a, con- 

 centric laminated nodules of lime carbonate ; h, homogeneous granules 

 partly lime carbonate, partly phosphatic ; c, inspissated fat com- 

 pounds. 



Fig. 8. Magn. 15 diam. Transverse section at the junction of head with neck 

 at the lower ends of the bulbs : a, body-constituents, similar to fig. 3, 

 a-d ; b, expanded visceral boundary forming a capsule to d, the bulbs 

 connected with the proboscides ; c, longitudinal water-vascular canals. 



Fig. 9. Magn. 100 diam. Transverse section through a portion of a sucker 

 adjacent to the skin : a, cuticular lining to sucker ; b, cuticle of skin of 

 head ; c, radiating muscular fibres special to sucker ; d, transverse en- 

 circling band ; e, fibrous capsule separating the special muscles from /, 

 the general parenchyma of the head. 



Fig. 10. Magn. 100 diam. A booklet near the base of proboscis, showing the 

 double contour and granular internal core. 



Fig. 11. Magn. 40 diam. Exserted proboscis as seen from the flat surface of 

 the head of the parasite. 



Fig. 12. Magn. 40 diam. Vertical section carried from before backwards 

 through an all but inverted proboscis : a, sucker ; b, its fibrous capsule ; 

 c, the radiating bands of muscle from the capsule into the general par- 

 enchyma of head ; d, sheath of proboscis ; e, cyhndrical layer of muscle 

 for jjrotrusion and evolving of proboscis ; /, circular layer limited to 

 region of booklets ; g, retractor muscle of proboscis. 



Fig. 13. Magn. 40 diam. Continuation downwards of former section to show 

 the termination of («) the retractor muscle in the central tendon (b) : 

 e, sheath ; d, radiating strong bands at the contraction of the sheath. 



Fig. 14. Magn. 40 diam. Further continuation of section into the upper end 

 of a bulb, to show the connexion of the fibres from the lower end of 

 central tendon with the bulb : a, special muscular band from central 

 tendon passing to the lower end of bulb and curving up on the opposite 

 side {b) to merge into the outer strata. 



Abothros carcharias, figs. 15-21. 



Fig. 15- Natural size, a, head ; b, point to which the outer cylinder of tissue 

 from the head covers the first segments of the colony, c. 



Fig. 16. Magn. 20 diam. Vertical section through iipper part of the head : a, 

 skin ; 6, inorganic layer ; c, parenchyma with strong longitudinal mus- 

 cular bands ; d, bulbs for retraction of proboscides, /; e, strong band con- 

 nected with the retaining in situ of the bulbs. 



Fig. 17. Magn. 20 diam. Vertical section through lower half of head: a, 

 colony of segmented zooids ; b, prolongation of the substance of head as 

 a cylinder of protection over the upper zooids ; c, radiating bands con- 

 necting the colony with the head ; d, fibrous boundary dividing the one 

 from the other. 



Fig. 18. Magn. 200 diam. About one third of^free end of proboscis: a, central 

 retractor muscle. 



Fig. 19. Magn. 15 diam. Transverse section through the head : a, body-con- 

 stituents ; b, fibrous capsule around the bulbs, c. 



Fig. 20. Magn. 20 diam. Front view of a segment about centre of the colony: 

 a, the line of distinction between one and the other, immediately above 



