FIGURE 2.211. SECTION OF THE HEAD OF THE LANCELET.
FIGURE 2.212. SECTION OF AN AMPHIOXUS-LARVA.
FIGURE 2.213. DIAGRAM OF PRECEDING.
FIGURE 2.214. SECTION OF A YOUNG AMPHIOXUS.
FIGURE 2.215. DIAGRAM OF A YOUNG AMPHIOXUS.
FIGURE 2.216. TRANSVERSE SECTION OF LANCELET.
FIGURE 2.217. SECTION THROUGH THE MIDDLE OF THE LANCELET.
FIGURE 2.218. SECTION OF A PRIMITIVE-FISH EMBRYO.
FIGURE 2.219. SECTION OF THE HEAD OF THE LANCELET.
FIGURES 2.220 AND 2.221. ORGANISATION OF AN ASCIDIA.