D I S C PHO RiE. 



CHAPTER FIRST. 



DISCOPHORiE IN GENERAL 



SECTION I. 



STRUCTURE OF THE DISCOPHOR-5:. 



The order of the Discoiohorae, as I believe it to be limited in nature, does not 

 embrace all the Acalephs referred to it by Eschscholtz, but only those which he 

 calls Discophor^ Phanerocarpje, and which Forbes has designated under the name 

 of Steganophthalmata, and Gegenbaur under that of Acraspeda. To these I think 

 some of the Cryptocarpae, such as the Charybdeidae and iEginidae, which were 

 but imperfectly known to Eschscholtz, must also be added. But, whatever be the 

 true limits of the subdivisions which the progress of science has rendered neces- 

 sary among the DiscophoriB, suice these Acalephs were first united as one group 

 b}^ Lamarck, and finally characterized as an order by Eschscholtz, so much is certain, 

 that there are two distinct types among them, differing widely in their structure 

 as well as in their mode of reproduction. I believe, however, that the true 

 principle upon which they may be distinguished has not yet been pointed out, 

 and that neither the presence nor the absence of a veil around the margin of their 

 disk, upon which Gegenbaur has based his division of the Craspedota and Acraspeda, 

 neither the exposed nor the protected position of the marginal eye-specks, which 

 Forbes has taken as a basis for the separation of the Steganophthalmata and Gym- 

 nophthalmata, nor the development of the ovaries and spermaries, upon which 



