EXPLANATION OF THE PLATES. 
5d, chorda, entire, 25 diam. 
20, 1852. 
Fig. 5c. 
same as fig. 3. 
Laid July 10, opened July 
Chorda, near the anterior end, 500 diam. The 
Fig. 6. Blood corpuscles from the vena terminalis, 40 diam. 
Laid July 18, opened July 28, 1852. 
Fig. 7.. Blood corpuscles; a, 6, in a natural state; ¢ to /, 
altered by water; a to 7, 500 diam.; 7, 1100 diam. 
About 18 days old. 
Fig. 8. Blood corpuscles from an adult; a, 6, c,d, e, ina 
natural state; h, altered by water, and dried; the others 
in water; a, b, c, 1100 diam.; the others, 500 diam. 
Fig. 9, 10, 11,12. Blood corpuscles; fig. 9, from the yolk; 
fig. 10, from the allantois; a,b, end views; c, c’, side views, 
showing the thickness ; 500 diam.; fig. 11, from the body: 
a, 1100 diam., as thick as broad; b, the same as a, 500 
diam.; c, d, end views; e, with two mesoblasts ; 500 diam. ; 
fig. 12, flat corpuscles from the allantois: a, 1100 diam. ; 
b, 500 diam. Period of laying unknown, opened Aug. 
25, 1852. 
Fig. 13 to 13e. Blood corpuscles, 500 diam.; fig. 13, flat- 
tened against each other; fig. 13a, a corpuscle squeez- 
ing between two others; fig. 13b, drawn out; fig. 13c, 
in a natural state, the left one seen edgewise, the middle 
one, from the side, the right one seen endwise. Laid 
June 12, opened Aug. 16, 1855. 
Fig. 14. Bloodvessel from the pia mater, 500 diam.; a, 6, 
Hatched in Oct. 1855. 
Cells of the olfactory nerve, close to the Schnei- 
mesoblasts in profile. 
Fig. 15. 
derian membrane, 500 diam.; a, 6, nearly perfect nerve 
tubules. Hatched in Oct. 1855. 
Fig. 16. From the hemisphere of the brain, section in pro- 
file, 500 diam.; a, outer stratum; 0, c, inner strata of 
the cells of the pia mater; d, blood corpuscles; e, cells 
of the hemisphere; the same as fig. 15. 
Fig. 16b. Cells at the surface of the hemisphere in profile ; 
fig. 16c, cells of the hemisphere from the interior ; a, single 
cells; b, b/,c, c!, altered by water; b, and c, the same 
cell seen from two different points of view, and magni- 
fied 1100 diam.; the others, 500 diam. Period of laying 
unknown, opened Sept. 6, 1852. 
Fig. 17, 17a, 17b. Cells of the olfactory nerve, just before 
the olfactory lobe; fig. 17, cells at various depths; fig. 
17a, at one focus, the surface of the cells; fig. 17b, a little 
deeper, so as to show the thickness of the walls; 500 
diam. ; the same as fig. 15. 
Fig. 18. Cells of the olfactory lobe; a, caudate cell, 500 
diam. ; the same as fig. 16b; fig. 18a, cells of the pia 
mater of fig. 18; 500 diam. 
Fig. 19. Cells of the Schneiderian membrane ; a, in a nat- 
80 
633 
ural state; 19, altered by water; 6, single cells of 19 ; 
500 diam.; the same as fig. 16b. 
Fig. 20. Cells of the medulla oblongata; a, a, caudate cells ; 
b, nearly filled by the mesoblast ; 500 diam.; the same as 
fig. 16b. 
Fig. 21. 
oblongata, 500 diam.; the same as fig. 16b. 
Fig. 22. Chorda dorsalis, 500 diam. Laid July 18, opened 
July 27, 1852. 
Fig. 23. Passage of muscles into cartilage, from the dorsal 
Cells from the spinal cord, just behind the medulla 
arch ; a, b, muscle; c, cartilage cells; 500 diam. Period 
of laying unknown, opened Aug. 25, 1852. 
Fig. 24. Muscular fibre macerated in water ; a, transverse 
section; 500 diam.; the same as fig. 25. 
Fig. 25. Muscular fibre from the foreleg; a, fibre ; 0, 
beaded fibrille ; 800 diam.; the same as fig. 16b, ete. 
Fig. 26. Tendinous fibrille ; fig. 26a, in a contracted state ; 
500 diam.; the same as fig. 16b. 
Fig. 27. Muscular fibre from the upper retractor muscles 
of the head, 800 diam.; fig. 27a, a beaded fibril, 1100 
diam. Laid June 21, opened Oct. 19, 1855. No fig. 28. 
Fig. 29. 
b, single cell; fig. 29a, surface view; 500 diam. Period 
Cells of the gall cyst, in profile; a, outer surface ; 
of laying unknown. Just hatched. 
Fig. 30. Cells of the ovary, 500 diam. Period of laying 
Just hatched. 
Cells of the liver; a, group; J, 0, single cells; 
500 diam. Period of laying unknown. Just hatched. 
Fig. 32. Liver cells; a, single cells; 32, a group, 500 
diam. ; 4, c, in water, 500 diam.; b/, c’, 1100 diam.; the 
same as fig. 16b. 
Fig. 33. Contents of the gall cyst, 500 diam. Period of 
laying unknown. Just hatched. 
Fig. 34. Contents of the gall cyst, 500 diam. Laid June 
21, opened Oct. 17, 1855; a to h, blood corpuscles, in 
unknown. 
Fig. 31. 
various stages of development; 7, decomposing globules. 
Fig. 35. First faecal discharge, 36 hours after hatching, 500 
diam. ; fig. 35a, crystals of uri¢ acid in the feces, color 
greenish-yellow, 800 diam. ; a, 0, c, d, e, f, various com- 
binations of erystals. 
PLATE XX. 
{Drawn from nature, by H. J. Clark.] 
All the figures are from Chelydra serpentina. 
Fig. 1, 1a, 1b. Uriniferous tube ; fig. 1, seen endwise; fig. 
la, seen at the bend; fig. 1b, at the side; 500 diam. 
Period of laying unknown, opened Aug. 31, 1853 
