CONTENTS OF PART FIRST 



Introduction ..... 

 Types of cleavage and gastrulation 

 Formation of the mesoderm 

 Body cavity 



Chapter I. Porifera. By K. Haider 

 I. Amphiblastula type . 

 II. Coeloblastula type 

 III. Parenchymula type . 



Development of Spongilla 



General considerations on the development 



teniatic position of the Porifera 

 Origin of the different types of canal system 

 Non-sexual reproduction of sponges 

 Development of the gemmula 

 Literature .... 



Chapter II. Cnidahia. 



Systematic . 



I. Hydrozoa . 



By K. Heider 



Medusae 



2. 



///;/ 



Hydroidea .... 

 Development of metagenetic 

 Budding of Hydroid polyps 

 Development of the Medusa 

 Comparison of polyp and Medusa 

 Budding and division in Medusee 

 Frustulation .... 

 Development of polyps with sessile gonophores 

 Development of hypogenetic Medusae 

 Developmental cycle of the Cuninas 

 Siphonophora ..... 

 Systematic ..... 

 («) Physophoridse 



Disconula larva of the Velellidse 

 Laws of budding in the Siphonophore 

 stock 

 (h) Calycophoridse 



General considerations on the origin of 

 the Siphonophora . . . . . 

 ix 



and 



sys 



1 

 3 



10 

 11 



13 



14 

 20 

 22 

 25 



28 

 30 

 82 

 34 

 36 



39 

 39 



39 

 39 

 40 

 43 

 43 

 4.5 

 48 

 49 

 50 

 53 

 58 

 59 

 59 

 60 

 65 



66 

 68 



