Comp"rison of bran"hial lamellæ of Scorpion and Ammocœtes, [175]

Comp"rison of bran"hial segments of Ammocœtes and Petromyzon, [169]

Comp"rison of Cephalaspidian and Palæostracan fish, [31]

Comp"rison of Cœlom of Peripatus and Vertebrate, [400]

Comp"rison of dermal covering of Pteraspis with chitin of Limulus or dentine of fish scales, [346]

Comp"rison of entosternite or plastron of Limulus with trabeculæ of Ammocœtes, [145]

Comp"rison of excretory organs of vertebrates and invertebrates, [389]

Comp"rison of gut of Arthropod and tube of central nervous system of Vertebrate, [43], [244], [433], [440], [455], [457]

Comp"rison of head-shield of Cephalaspis and Ammocœtes, [291], [329], [338]

Comp"rison of hypophysial tube with olfactory tube of Arthropod ancestor, [229]