
EXPLANATION 
Fig. 17. A gland of the stomach in profile; a, surface of the 
stomach ; } above, opening of the gland; in the middle and 
below, its cavity ; c,d, its walls; 500 diam. Just hatched. 
Fig. 18. 
a’, columns of cells of the mucous membrane; 3, stratum 
Section across the thick intestine, 500 diam.; a, 
of round cells: c, inner, and d, outer muscular coats; ¢, 
thin membrane inclosing the whole intestine; fig. 18a, 
the same as fig. 18, a, and a’, being seen in one focus; 
fig. 18b, two columns of cells separated so as to disclose 
the mesoblasts ; fig. 18c, a, b, cells of fig. 18, segmenting ; 
the same as fig. 17. 
Fig. 19. Section across the long intestine, 500 diam.; a, 3, 
c, d, e, as in fig. 18; the same as fig. 17. 
Fig. 20. One of the claws, 25 diam.; a, horny sheath; 0, 
interior cells of the claw; 1’, cells at the base of the claw; 
fig. 20a, cells of the horny sheath, 500 diam., in profile ; 
fig. 20b, the same as fig. 20a, view perpendicular to the 
surface ; fig. 20c, cells at the end of the horny sheath, 500 
diam.; fig. 20d, cells of the skin of the next joint, just 
beneath the sheath, 500 diam. Period of laying un- 
known, opened Aug. 25, 1852. 
Fig. 21. The bone of the claw, 40 diam.; fig. 21a, cells at 
the surface of fig. 21, 500 diam.; the same as fig. 20. 
Fig. 22. 
diam. ; fig. 22a, separate cells of fig. 22. 
Cartilaginous matrix of a bone of the toe, 500 
Period of lay- 
ing unknown, opened in Sept., 1852. 
Fig. 23. Cells at the surface of the foot, 500 diam.; the 
same as fig. 22. 
Fig. 24. 
as fig. 22. 
Piece of the bone of the toe, 500 diam.; the same 
Fig. 25. Interior cells of the foot, 500 diam.; the same as 
fig. 22. 
Fig. 26. Cells of the shield, 500 diam.; the same as fig. 22. 
Fig. 27. Cells of the ear, 300 diam. Laid July 18, opened 
July 28, 1852. 
Fig. 28. Cells of the eye, 300 diam.; a, cells of the retina; 
b, skin of the head; c, passage-way to the brain; the 
same as fig. 27. 
Fig. 29. 
rounding membranes, 40 diam. ; a, membrana pupillaris; 
Crystalline lens taken out of the eye with the sur- 
b, pigment layer on the zonula Zinnii (c). Period of lay- 
ing unknown, opened in Aug. 1852. 
Fig. 30. Portion of the crystalline lens, 300 diam.; a, the 
converging ends of the fibres 6; the same as fig. 22. 
Fig. 31. The converging ends of the fibres of the crystalline 
lens, 300 diam.; the same as fig. 29. 
Fig. 32. Part of a section through the centre, from front to 
back, of the crystalline lens; a, the ends of the fibres, 40 
diam. ; fig. 32a, a, b,c, d, four fibres of fig. 32, 500 diam. ; 
fig. 32b, large globules intermixed with the fibres, 500 
OF THE PLATES. 


635 
diam. ; fig. 32c, portion of a fibre twisted so as to show 
a combined view of the edge and of the flat side, 500 
diam. ; fig. 32d, ends of fibres swollen by water, 500 diam. 
Period of laying unknown, opened Sept. 9, 1852. 
Fig. 33. 
midway between the front and back of the eye, 500 
Section of the thickness of the retina at a point 
diam. ; 6, c, cells of the inner or first layer; d, second 
layer; e, f, third layer; g, fourth layer; h, 7, membrana 
Jacobi; i’, outer prolongations of h and 7; fig. 33a, cells 
of the membrana Jacobi, with their yellow and orange 
mesoblasts, 1100 diam. Hatched Oct. 1855. 
Fig. 34. Profile of the mucous membrane of the thick intes- 
tine, 500 diam. ; fig. 34a, surface view of fig. 34, altered by 
water ; b, a group; ¢, single cell; 500 diam.; the same as 
fig. 15. 
15, and erroneously marked 20 and 20a. 
These two figures are between fig. 14 and fig. 
PLATE XXII. 
[Drawn from nature, by H. J. Clark.] 
Fig. 1, from Thalassochelys Caouana ; fig. 7, from Trache- 
mys serrata; all the others from Chelydra serpentina. 
Fig. 1. 
innermost cartilage cells; a’, a’, a’, successively nearer to 
Obliquely transverse section of a rib, 500 diam.; a, 
the surface of the bone ; }, innermost layer of the fibrous 
layer next to the cartilage cells; }, c,d, e, f, g, succes- 
sively nearer to the surface of the bone; h, corium; g', 
granular, hardened fibrille of the outer layer of the bone ; 
i, similar soft fibrilla: of the corium ; fig. 1a, a single car- 
tilage cell, 800 diam.; a, parietes of the blastematous cay- 
ity; 0, cell wall shrunk; c, mesoblast; fig. 1b, the same 
as fig. la, 1100 diam. Just hatched. 
Fig. 2. Transverse section of a rib; the letters are the same 
as in fig. 1. 
Fig. 3. 
diam., view from within ; a, fibres running in the direc- 
Strip from the inferior face of a vertebra, 500 
tion of the length of the vertebra; b, more interior layer ; 
c, still deeper; d, innermost layer; fig. 3a, granular 
fibrillz of fig. 3, b, 800 diam. Just hatched. 
Fig. 4.. Transverse section of the interior portion of the 
ventral half side of a vertebra, 500 diam.; a, 6, granular 
lining of cells; c, ossification eneroaching upon the cells; 
d, coarse granular ossification ; e, mesoblast of the cells; 
the same as fig. 3; fig. 4a, a, b, crystals of nitrate of lime. 
Fig. 5. Transverse section of the cartilage cells of the cor- 
acoid bone, 500 diam.; a, blastema; 0, cells. Just ready 
to hatch. 
Fig..6. Longitudinal section of fig. 5; a,b, the same as in 
