FIGURES 2.236 AND 2.237. Ascula of Gastrophysema.

FIGURE 2.238. Olynthus.

FIGURE 2.239. Aphanostomum Langii.

FIGURES 2.240 AND 2.241. A TURBELLARIAN.

FIGURES 2.242 AND 2.243. Chaetonotus.

FIGURE 2.244. A NEMERTINE WORM.
FIGURE 2.245. AN ENTEROPNEUST.
FIGURE 2.246. SECTION OF THE BRANCHIAL GUT.
FIGURE 2.247. THE MARINE LAMPREY.
FIGURE 2.248. FOSSIL PRIMITIVE FISH.