94 PROFESSOR RAY LANKESTER. 
EXPLANATION OF PLATE VII, 
Illustrating Professor Ray Lankester’s memoir on “ Green 
Oysters.” 
Fies. 1 to 8.—Various specimens of Navicula ostrearia, Gaillon, 
as seen in the living condition. 
Figs. 2 and 4 show that face of the specimen in which one endochrome 
band only is seen; the other figures give a plane at right angles to 
this. a. Nucleus. 6. Colourless protoplasm near the nucleus (so- 
called ‘‘cross-band”). ¢. Endochrome band. d. Blue-pigmented 
protoplasm. e. Refringent spherule, apparently deeply coloured by 
Marennin (the blue pigment). .f Siliceous cell-wall. g. Vacuole. 
Fic. 9.—A specimen of Navicula ostrearia, during the action of dilute 
ammonia. 4h. Broken particles of the blue-coloured cell-substance. 
Fic. 10.—Specimen of a “ Huitre de Marennes,” of full colour. Natural 
size. The right shell-valve has been removed, and the right lobe of the mantle 
reflected so as to expose the green-coloured branchial plates and the four 
labial tentacles. (From a coloured sketch executed from nature by Miss A. 
Stone in the zoological laboratory of University College, London.) 
Fie. 11.—Transverse section of a portion. of a gill-plate of an oyster (green 
specimen), to show the arrangement of the gill-bars or gill-filaments and the 
position of the secretion-cells on their surface. 7/s. Inter-lamellar water- 
space. i/j. Inter-lamellar junction. w. Aperture between neighbouring 
filaments, by which water passes into the inter-lamellar space. ¥. Gill-bars or 
filaments. mj. The “main bars” or “great filaments,” interposed between 
projecting groups of minor filaments. cf. The chitinous internal skeleton of 
the gill-filaments. ¢. The epithelium of the inter-lamellar space. Jac. The 
lacunar tissue. gl. The secretion cells, which are the seat of the green 
colour. 
Fic. 12.—A transverse section of two minor gill-filaments, more highly 
magnified. gl. The green-coloured secretion-cells. ch. The chitinous skeleton. 
éc. Blood-corpuscles in the lacunar tissue. ch. Nucleus of the chitinous 
skeleton. fe. Frontal epithelium. J/e. Lateral epithelium. e. Posterior 
epithelium (epithelium of the inter-lamellar surface). 
Fic. 13.—Portion of a single gill-bar, isolated by teazing and seen from the 
side, to show the rows of green-coloured secretion-cells (g/.). Letters as in 
Fig. 12. 
Fic. 14.—Isolated secretion-cells from the gills and labial tentacles of a 
green oyster, more highly magnified. The seven upper figures as separated 
by teazing, the four lower figures as found naturally separated and adherent to 
the free surface of the gill-lamella. 
