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.