EXPLANATION OE PLATE N— continued. 



Fig. 5. Fragment of the outer lamella of an inner gill -plate, sbowin" 

 two interlamellar junctions, stomata of the water- passages and "-ill- 

 filaments here and there exposed by tearing off the sublilamentar tissue. 

 Seen from the deep or interlamellar surface with a hand lens (from a 

 drawing by Mr. Lankester). 



Fig. 6. — Tranverse section of a portion of an outer gill-plate taken 

 near the apex or free angle (see Plate IV, fig. 10). The interlamellar con- 

 crescence is not limited as in sections across the middle level of the "ill, 

 to definitely disposed interlamellar junctions. Low power. 



Fig. 7. — Transverse section of a portion of an outer gill-plate, still 

 nearer to the angle of the plate. Tiie regular concrescence on the right- 

 hand side of the section is noteworthy. The section, thougli at ri^-ht 

 angles to the filaments, approaches on this side nearer to the angle of the 

 gill-plate than it does on the left-hand side. Low power. 



Fig. 8. — Diagrammatic view of a block cut from the outer lamella of 

 the outer gill-plate when not functioning as a brood-pouch, seen from 

 the interlamellar surface. This figure tihows the relation of the water- 

 passages and their stomata to the interfilamentar spaces, and is intended 

 to render the transverse sections given in other figures intelligible (from 

 a drawing by Mr. Lankester). 



_ Fig. 9. — Highly magnified view of a portion of such a section as that 

 given in fig. 2. 



Fig. 10. — A similarly magnified view of a portion of fig. 1. 



Fig. 11. — A similarly magnified view of a portion of fig. 3. 



Fig. 12 — A transverse section of a single filament taken behceen the 

 horizons of transverse interfilamentar junction, and at a point where the 

 subfilamentar outgrowth is least prominent or developed. Obj. 8, oc. 4. 



Fig. 13. — Transverse section through two filaments and subjacent 

 subfilamentar tissue taken at the horizon of a transverse interfilamentar 

 junction. The reduction of the chitinous rods, the continuity of the 

 chitinous deposit with the transverse fibres and the character of the 

 subfilamentar lacunar tissue, are well seen. 



PLATE VI.— Anodon (except fig. 24, 30, and 31). 



Fig. 14. — Longitudinal section parallel with the surface of the lamella 

 and passing through the horizon of the chitinous rods. The external 

 stomata of the water-passages, the transverse and the obliquely -crosmuj 

 elements of the fibrous interfilamentar junctions are shown, as well as 

 the continuity of the chitinous rods. 



Fig. 15. — A similar section taken more deeply, so as to lie in the 

 horizon of the subfilamentar mass of lacunar tissue which grows out 

 from the deep surface of the filaments. It shows the lumina of the 

 water-passages in section and the lacunar tissue with its spaces blocked 

 to some extent by yellow granular food-material destined for the Glo- 

 chidian embryos. 



Fig. 16. — A more highly magnified view of a similar section taken 

 somewhat deeper (near the interlamellar or subfilamentar surface of the 

 lamella), and thick enough to show the tapering of the water-passages 

 towards their interlamellar openings, windows, or stomata. 



Fig. 17. — Diagram of a block of the inner lamella of the outer gill- 

 plate, cut vertically through an interfilamentar region, and exposing the 

 interior of three water-passages. The forward position of the fibrous 

 interfilamentar junctions itrf.) is seen, and the great depth and bulk of 

 the mass of concreted subfilamentar tissue rendered obvious. (From a 

 drawing by Mr. Lankester.) 



Fig. 18. — A fragment of a subfilamentar outgrowth in section, to 



