Studies from the Biological Laboratory

adult Amphioxus ancestors Annelids appear appendicularia Arachnids arterial pressure atriopore bacilli believe blastopore blood body bottom brain cavity Chiton copepods corneal hypodermis cross-section crustacea delamination digestive tract diverticula divided division Dohrn dorsal echinoderms ectoblast embryo embryology fauna fibrinogen figure fourth pair ganglion gill-slits groups hydroids hypodermis invagination lancelets larva larvæ larval form later stage macromeres median mesoblast metazoa mid-gut middle layer middle line muscle myotomes Nauplius nerve nuclei ocean outer pair of appendages pair of ganglia pair of ventral pair of walking Pallene Pantopod-larva passes pelagic pelagic animals pharynx Phoxichilidium pigment layer plane Plate posterior pre-oral primitive pelagic proboscis proteids protoplasm Pycnogonids rarefaction retinal elements Sea-Spiders second pair seen segments serum albumin shown by Fig side species Spiders stomodæum structure surface views Tanystylum thickenings third pair tion trace Trochophore tunicates ventral ganglia ventral organs vertebrates walking legs yolk