DICYEMIDÆ.--The Infusoriform larva (vol. II. fig. 62). PORIFERA.--(_a_) The Amphiblastula larva (fig. 215), with one-half of the body ciliated, and the other half without cilia; (_b_) an oval uniformly ciliated larva, which may be either solid or have the form of a vesicle. COELENERATA.--The planula (fig. 216). TURBELLARIA.--(_a_) The eight-lobed larva of Müller (fig. 222); (_b_) the larva of Götte and Metschnikoff, with some Pilidium characters. NEMERTEA.--The Pilidium (fig. 221). TREMATODA.--The Cercaria. ROTIFERA.--The Trochosphere-like larvæ of Brachionus (fig. 217) and Lacinularia. MOLLUSCA.--The Trochosphere larva (fig. 218), and the subsequent Veliger larva (fig. 219). BRACHIOPODA.--The three-lobed larva, with a postoral ring of cilia (fig. 220). POLYZOA.--A larval form with a single ciliated ring surrounding the mouth, and an aboral ciliated ring or disc (fig. 228). CHÆTOPODA.--Various larval forms with many characters like those of the molluscan Trochosphere, frequently with distinct transverse bands of cilia. They are classified as Atrochæ, Mesotrochæ, Telotrochæ (fig. 225 A and fig. 226), Polytrochæ, and Monotrochæ (fig. 225 B). GEPHYREA NUDA.--Larval forms like those of preceding groups. A specially characteristic larva is that of Echiurus (fig. 227). GEPHYREA TUBICOLA.--Actinotrocha (fig. 230), with a postoral ciliated ring of arms. MYRIAPODA.--A functionally hexapodous larval form is common to all the Chilognatha (vol. II. fig. 174). INSECTA.--Various secondary larval forms. CRUSTACEA.--The Nauplius (vol. II. fig. 208) and the Zoæa (vol. II. fig. 210). ECHINODERMATA.--The Auricularia (fig. 223 A), the Bipinnaria (fig. 223 B), and the Pluteus (fig. 224), and the transversely-ringed larvæ of Crinoidea (vol. II. fig. 268). The three first of which can be reduced to a common type (fig. 231 C). ENTEROPNEUSTA.--Tornaria (fig. 229). UROCHORDA (TUNICATA).--The tadpole-like larva (vol. III. fig. 8). GANOIDEI.--A larva with a disc with adhesive papillæ in front of the mouth (vol. III. fig. 67). ANURUS AMPHIBIA.--The tadpole (vol. III. fig. 80). [FIG. 215. TWO FREE STAGES IN THE DEVELOPMENT OF SYCANDRA RAPHANUS. (After Schultze.) A. Amphiblastula stage. B. Stage after the ciliated cells have commenced to be invaginated. _c.s._ segmentation cavity; _ec._ granular epiblast cells; _en._ ciliated hypoblast cells.] [FIG. 216. THREE LARVAL STAGES OF EUCOPE PLOYSTYLA. (After Kowalevsky.) A. Blastosphere stage with hypoblast spheres becoming budded into the central cavity. B. Planula stage with solid hypoblast. C. Planula stage with a gastric cavity. _ep._ epiblast; _hy._ hypoblast; _al._ gastric cavity.]