CONTENTS. 



Ctenophora. 



Page 



Introduction j 



I. Tjalfiella tristoina Mrtsn 3 



A. Anatomj- and Histology' of the grown animal 6 



B. Development; Anatomy of the Cydippid-stage i6 



C. Regeneration 24 



D. Affinities of Tjalfiella 25 



E. Phylogeny 37 



II. The pelagic Ctenophora of the Northern Atlantic 60 



1. Mertensia ovum (Fabricius) 60 



2. Pleurobrachia pileus (O. F. MUll.) 68 



3. — crinita Moser yj 



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



5. Beroe cucumis Fabricius , 83 



Hormiphora plumosa (M. Sars) , 88 



Lesueuria vitrea M. Edw 89 



Cestus veneris Lesueur gi 



Beroe Forskalii Chun . g2 



Zoogeographical Remarks g 



2 



