Studies from the Biological Laboratory

abdomen adult Amphioxus ancestors Annelids appear appendicularia Arachnids ascidians atriopore bacilli believe blastopore blood body bottom brain cavity chitin copepods corneal hypodermis cross-section Crustacea delamination digestive tract diverticula divided division Dohrn ectoblast ectoderm embryo embryology fauna fibrinogen figure fourth pair ganglion gill-slits groups hydroids hypodermis inner ends inner layer invagination lancelets larva larvæ larval form later stage maceration macromeres median mesoblast metazoa mid-gut middle layer middle line muscle myotomes Nauplius nerve nuclei œsophagus outer ovigerous legs 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 protoplasm Pycnogonids raphe retinal cells retinal elements Sea-Spiders second pair seen serum shown by Fig side species Spiders stomodæum structure surface views Tanystylum thickened third pair tion trace Trochophore tunicates ventral ganglia ventral organs vertebrates walking legs yolk