C TEN P H RiE. 



CHATTER FIRST. 



CTENOPHOR.E IX GP:NERAL. 



SECTION I. 



STRUCTURAL FEATURES OF THE CTEXOPHOR.E IN GENERAL. 



I NEED not repeat here what I have stated in the first part of this vohime 

 respecting the affinities of the Ctenophora?. They are unquestionably Radiates 

 belonging to the class of Acalephs, in which they form a natural order. This 

 being admitted, it remains now for me to present a sketch of their structui-al 

 peculiarities, in conformity with their general and special homologies, and an outline 

 of their mode of life founded upon a knowledge of their special structure.^ 



^ We are indelited to Gegenbaur for the latest 

 ami most comprehensive summary of wliat is now 

 known about Ctenophorte. It is therefore proper, 

 that whatever critical remarks I may have to 

 present upon the views entertained by other natu- 

 ralists, respecting this group of animals, should be 

 made with special reference to his j^aper, " Studien 

 iiber Organisation und Systematik der Ctenophoren," 

 in " Archiv fiir Naturgeschichte, 185G," 1 vol. p. 

 163. Gegenbaur, with Leuckart, considers them 

 as constituting one harmonious primary group with 

 the Medusx, Ilydroids, and Anthozoa, called Coe- 



lenterata by the latter. I have already presented 

 my objections to the separation of the Coclenterata 

 and Echinodermata as two distinct primary divisions 

 of the animal kingdom, upon the broad ground 

 that these divisions do not differ in the j^lan of 

 their structure, but simply in the mode of execution 

 of that plan (pp. 64-72) ; and it onlj' remains for 

 me to show that the structure of all these animals is 

 strictly homological, and to remind those naturalists 

 who may feel inclined to regard the distinction 

 between a plan of structure and its mode of exe- 

 cution as of secondary importance, or as an inno- 



