CHAPTER XII. CHÆTOPODA.✦

Formation of the germinal layers, pp. 319-325. The larval form, pp. 325-338. Formation of organs, pp. 338-342. Alternations of generations, pp. 342, 343.

CHAPTER XIII. DISCOPHORA.✦

Formation of layers, pp. 347-350. History of larva, pp. 351-354.

CHAPTER XIV. GEPHYREA.✦

Gephyrea nuda, pp. 355-361. Gephyrea tubicola, pp. 361-364. General considerations, p. 364.

CHAPTER XV.✦

Chætognatha, pp. 366-369. Myzostomea, pp. 369, 370. Gastrotricha, p. 370.

CHAPTER XVI.✦

Nematelminthes, pp. 370-379. Acanthocephala, pp. 379-381.

CHAPTER XVII. TRACHEATA.✦

Prototracheata, pp. 382-387. Myriapoda, pp. 387-395. Insecta, pp. 395-429. Embryonic membranes and the formation of the layers, pp. 400-406. Formation of the organs, pp. 406-417. Special types of larvæ, pp. 417-419. Metamorphosis and heterogamy, pp. 420-429. Arachnida, pp. 431-455. Formation of the layers and general development, pp. 431-446. Formation of the organs, pp. 446-455. Formation of the layers and embryonic envelopes in the Tracheata, pp. 456-458.

CHAPTER XVIII. CRUSTACEA.✦

History of larval forms, pp. 459-511. Branchiopoda, pp. 459-465. Malacostraca, pp. 465-487. Copepoda, pp. 487-492. Cirripedia, pp. 492-500. Ostracoda, pp. 500-502. Phylogeny of the Crustacea, pp. 502-511. The formation of the germinal layers, pp. 511-521. Comparative development of organs, pp. 521-529.

CHAPTER XIX.✦

Poecilopoda, pp. 534-538. Pycnogonida, pp. 538, 539. Pentastomida, pp. 539-541. Tardigrada, p. 541. Summary of Arthropodan Development, pp. 541-543.