X CONTENTS 



PAGE 



IL Anthozoa 75 



(a) Alcyonaria 75 



Cleavage, and the cleveloi^ment of the planula 76 



Attachment and development of the polyp . 77 



Budding 82 



(6) Zoantharia 88 



Cleavage and development of the planula . . 88 



Development of the septa 90 



Formation of the calcareous skeleton . . 98 



Division and budding 100 



III. Scyphomedusae 102 



(«) Lucernaridae ........ 102 



(b) Charybdeidae 103 



(o) Discophora ........ 103 



Alternation of generations in the Discophora . 105 



Development of the Scyphistoma . . . 105 



Strobilation 113 



Hypogenetic development of Pelagia . . 117 



Metamorphosis of the Ephj'ra ,. . . . 119 



General considerations regarding the Scypho- 

 medusae ........ 122 



General considerations regarding the Cnidaria 125 



Literature ........ 127 



Chapter III. Ctenophoka. By K. Heider .... 136 



Tectonic ........... 136 



Embryonic develoiDment 138 



Cleavage 139 



Epiboly 142 



Formation of the gastrovascular system ..... 146 



Development of the mesoderm ....... 148 



Metamorphosis 151 



Heterogeny . 153 



General considerations 154 



Literature 158 



Chapter IV. Platvhelminthes. By E. Korschelt . . . 159 



I. Turbellaria 159 



Systematic survey ; different forms of development . 159 



1. Polycladida 160 



A. Direct development. Ovijjosition; cleavage 160 



Formation of the germ-layers . . . 161 

 External and internal development of the 



body 163 



£. Indirect development ..... 165 



Müller's larva ; transition to the adult 



animal ....... 165 



Aberrant larval forms (Oligocladus, Sty- 



lochus pilidium) 167 



