Studies from the Biological Laboratory, Band 5

adult Amphioxus ancestors animal pole annelids anus appendicularia Arachnids arterial pressure ascidians atriopore blastomeres blastopore blood body bottom brain Branchiostoma cavity cells Chiton chordata ciliated copepods craspedota Cross-section crustacea digestive tract division Dohrn dorsal echinoderms ectoblast embryo embryology endostyle fauna fibrinogen figure fin-ray fishes furrow ganglion gastrulation gill-slits habit hydroids hypodermis inner intercostal invagination lancelets larva larvæ longitudinal section macromeres median fin medusæ mesoderm metazoa mid-gut middle layer middle line mouth muscle myotomes nerve normal notochord nuclei observed ocean outer pair of appendages pair of ganglia pair of walking Pallene Pantopod-larva pelagic pelagic animals pharynx Phoxichilidium pigment Plate posterior pre-oral chamber primitive pelagic proteids protoplasm Pycnogonids rarefaction retinal elements salpa seen segments serum albumin serum globulin shown in Fig side species specimens stage structure surface views Tanystylum third pair trace tunicates ventral ganglia ventral organs vertebrates walking legs yolk