Contents, 



page, 



Introduction 1 



Note on the Ontogeny of the "Trachornedusae" 4 



Embryology 9 



A, Dehiscence 10 



B, Periodicity 11 



C, Egg-envelope 15 



Methods 16 



D, Segmentation 18 



The Planula 21 



The hydra Larva 22 



A. Tentacles • ■ -- 24 



B. Form of Coelenteron 25 



Habits 27 



■Degeneration Phenomena 29 



Budding in the Larvae - Metagensis 30 



Transformation of the Polyp 59 



Youngest L!edusae; Arrangement of Tentacles 



and Sense-Organs 42 



Histogenesis of Marginal Organs. 



A, In the Lax'va 53 



