CONTENTS XI 



PAGB 



2. Tricladida. Oviposition ; yolk-cells ; cleavage . 169 

 Formation of the embryo and its organs . . 169 



3. Rhabdocoelidae 173 



[Acoela] . 175 



General considerations : relation of the Tur- 



bellaria to the Ctenophora (Cteno plana and 



Coeloplana) 176 



11. Trematoda 178 



Composition of the egg from egg-cells and yolk-cells . 178 



1. Distomidse 178 



Embryonic development 179 



Further course of development; Distomum 



hepaticum 180 



Sporocyst ; E,edia ; Cercaria .... 180 

 Differences in the development of various 



Distomidae 185 



Cercaria setifera, Bucephalus, Leucochlori- 



dium, etc. 186 



2. Polystomidse 188 



Diplozoon, Gyrodactilus, etc 189 



III. Cestoda 190 



Character of the eggs ; resemblance to those of Tre- 



matodes 190 



Embryonic development of the Bothriocephalidse . 191 



Embi'yonic development of the Tseniadse . . . 193 



Further development ; transference of the eggs ; 



cysticercus 194 



Formation of the scolex ; transference of the cysti- 

 cercus ; development of the tapeworm . . . 197 



General considerations : significance of the develop- 

 ment (Archigetes, Caryophyllseus, Amphiptyches, 



etc.) 198 



Taenia coenurus and T. echinococcus ; relation to the 



Trematodes (Amphilina) and Turbellaria . . 200 



Literature 201 



Chapter V. Orthonectid^ and Dicyemid^. By E. Korschelt 206 



I. Orthonectidae 206 



Systematic survey ; occurrence ; shape of the body ; 



organization; eggs 207 



Development of the male 208 



Development of the female 209 



II. Dicyemidae 209 



Systematic occurrence ; organization .... 209 



Development of the vermiform embryos . . . 210 



Structure and development of the inf usoriform embryos 211 



