DEVELOPMENT OF CUCUMARIA ECHINATA 945 
Fig. 13.—Very old gastrula to show the internal feature. Viewed from 
the right side. The archenteron has divided into hydro-enterocoele and 
gut, and the stomodaeum has appeared, x 200. 
Fig. 144.,—Posterior view of the cross-section cut along the plane | in 
fig. 13 to show the stomodaeum. x 200. 
Fig. 148.—Fifteenth section below the former in the same series, cut 
along the plane 2 in fig. 13. To show the posterior part of hydro-entero- 
coele and the gut separated from it. x 200. 
Fig. 15.—Early dipleurula viewed from the left side. The internal 
cavity as a solid body ; gut not represented. x 200. 
Fig. 164.—Posterior view of the cross-section cut along the plane 1 in 
fig. 15. x 200. 
Fig. 168.—Eleventh section below the former in the same series, cut 
along the plane.2 in fig. 15. x 200. 
Fig. 16c.—Fourth section below tlie former, cut along the plane 3 in 
fig. 15. x 200. 
Fig. 16p.—Seventh section below the former, cut along the plane 4 in 
fig. 15. +200. 
PLATE 9. 
Fig. 17.—Dipleurula viewed from the left side. The internal cavities 
shown as solid bodies ; gut not represented. x 200. 
Fig. 184.—Posterior view of the cross-section cut along the plane 1 in 
fig. 17. x 200. 
Fig. 188.—Sixteenth section below the former in the same series, cut 
along the plane 2 in fig. 17. x 200. 
Fig. 19.—Late dipleurula viewed from the left side. The internal 
cavities shown as solid bodies ; gut not represented. x 200. 
Fig. 204.—Posterior view of the cross-section cut along the plane 1 
in fig. 19. x 200. 
Fig. 208.—Twelfth section below the former in the same series, cut along 
the plane 2 in fig. 19. x 200. 
Fig. 214.—Karly doliolaria (no, 2 represented in Table II in the text) 
viewed from the ventral side. The internal cavities shown as solid bodies ; 
gut not represented. x 200. 
Fig. 218.—Same viewed from the left side. x 200. 
Fig, 224.—Posterior view of the cross-section cut along the plane 1 in 
fig. 21. x 200. 
Fig. 228.—Fourth section below the former in the same series, cut along 
the plane 2 in fig. 21. x 200. 
Fig. 22c.—Third section below the former, cut along the plane 3 in 
fig. 21. x 200. 
Fig. 22p. Sixth section below the former, cut along the plane 4 in 
fig. 21. x 200. 
$2 
