11 Y D R I D yE. 



CHAP T E K F 1 11 S T . 



C II Y N E AND ALLIED IVI E D U S yE 



SECTION I . 



GENERAL REMARKS UPOX IIYDROIDS AND NAKED-EYED MEDUSTE. 



As the liicts bearing upon the genetie connection and /.oijhjgical allinities of 

 the Hydroids and certain Medusas, which have been described as independent ani- 

 mals, are not yet sufliciently known, or generally acknowledged, to be made tiie 

 basis of comprehensive generalizations, I find it necessary, in this ])ait of my work, 

 to adopt a different method of presenting my subject, from (hat j)iirsue(| in the 

 preceding chapters. Thus far, when considering the representatives of tlu; (Jlejio- 

 phora) and Discophoraj, I have found it possible to discuss their natural affinities, the 

 combinations of their structural elements, their mode of development, and their 

 special classification, without regard to the contributions I have had an op[)ortunity 

 of making myself to their Natural History. But respecting the order of llydroidas, 

 in which I have been led to include animals thus far considered as widely different 

 from them, I am compelled to adopt another course, and first, to describe, minutely, 

 those which I have had an opportunity of examining, before I proceed to discuss 

 their natural relations. To avoid misapprehensions, however, I will here briefly state, 

 that I see no reasons for separating, as distinct equivalent groups, the Siphonophorae 

 from the naked-eyed Medusa3 and Ilydroids proper; nor do I believe any of these 

 animals to be more closely allied to the Polyps than to the higher Acalephs. Even 



