CONTENTS. 



DISTRIBUTION 



1. Distribution in Space .... 



a. Horizontal Distribution . 

 h. Vertical Distribution 



General Considerations 

 Bathimetrical Zones 

 The Surface Zone 

 The Littoral Zone 

 The Laminarian Zone 

 The Coralline Zone 

 The Deep-water Zone 

 The Abyssal Zone 

 Deep Lacustrine Fauna 



2. Distribution in Time .... 



Fossils referred to the Hydroida on insufficient Evidence 



Fossil Ilydroid Trophosomes . 



Fossil liydroid Medusse 



Graptolites .... 



Table of the Distribution of the Hydroida in Time 



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SUPPLEMENTARY. 

 CLASSIFICATION .... 

 HOMOLOGIES OF THE CCELENTERATA 



TERATOLOGY AND PATHOLOGY 



1. Modifications resulting from Parasitism 



2. Other Abnonnal Conditions 



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