CONTENTS. 



Ctenophora. 



Page 



Introduction i 



I. Tjalfiella tristonia Mrtsn j 



A. Anatom}- and Histology of the grown animal 6 



B. Development; Anatomj' of the Cydippid-stage i6 



C. Regeneration 24 



D. Affinities of Tjalfiella 25 



E. Phjlogeny 37 



II. The pelagic Ctenophora of the Northern Atlantic 60 



1. Mertensia ovum (Fabricius) 60 



2. PleurnVirachia pileus (O. F. Mull.) 68 



3. - crinita Moser 75 



4. Bolina infundibuluni (O. Fr. Miiller) 75 



5. Beroe cucuniis Fabricius 83 



Hormiphora plumosa (M. Sars) 88 



Lesueuria vitrea M. Edw 89 



Cestus veneris Lesueur 91 



Beroe Forskalii Chun 92 



Zoogeographical Remarks 92 



