gg- LUCERiNAUIyE AND THEIR ALLIES. 



development, among the pigment spots of the CorynitUt, up to the unmistakably 

 refracting, and, we doubt not, image-forming, plano-convex lenses of Aurclia.' 

 Now although we have never been able, after the most diligent search, to discover 

 a trace of a nervous fibre in Aurelia, yet its optical apparatus is so undeniably an 

 or^an of vision that a special nervous localization seems inevitable. Unfortunately 

 for our wishes, Aurelia does not stand so high among the members of its grand 

 division as to be subjected to that kind of differentiation which segregates the 

 nervous matter from the surrounding mass and puts the cell-mark upon it. If then 

 Aurelia fails in tliis respect, what can we expect to find in Lucernarite, with their 

 ill-defined eye-spots, but a far less developed nervous system, and still more diffused 

 and undefined areas of nervous power I 



§ 18. The Reproductive System. 



132. Differentiation. — Of the two main points of difference between the Lucer- 

 nariiE and the Strobiloida, the character of the reproductive system is scarcely 

 second in importance. It is, beyond all question, unparalleled in concentration 

 and differentiation, and is unique in design. But, as if these were not enough, 

 there is added to one form of specialization another none the less marked, and 

 certainly more conspicuous, in a total separation of the reproductive stroma from 

 the mass of the umbellar parietes. The strata which inclose the eggs or sperma- 

 tozoa have no part in forming the bulk of the umbella ; they are mere appendages 

 moulded into the form of globular sacs, and attached in the same way as the digitidi 

 to the circumoral face. 



133. In the Strobiloida the reproductive material is imbedded in the general 

 mass which forms the parietes of the umbella. The region of their genital organs, 

 it is true, is specialized after a certain model, but it does not make it any the less 

 a part and parcel of the boundary-wall of the general cavity of the body. We 

 wish it to be clearly understood here that, when speaking of the Strobiloida, we do 

 not include the Charybdeidit; in that order. Where the latter belong, in our 

 opinion, may be found in the chapter (Part XI) on their morphology and in the 

 one devoted to ordinal characters (Chapter XIII). 



134. The sexes of the Lucernarise are separate, but the structure of the saccules 

 of both is identical. In description of the topographical position and the homo- 

 logical relations of the various organs to each other and to certain parts of the 

 body, we have given all the general information that is necessary to a perfect 

 understanding of the site of the reproductive system (^ 50), its general outlines, 

 appendages (^f 52), arrangement, and relative age of the saccules (1J 51). The 

 structure, shape, and peculiar position of these organs remain yet to be given in 

 detail. 



l;)5. Structure of Saccides.— In' a previous paragraph (116) of the section on 

 the di,(iiMi, we have described a singular attitude which these bodies sometimes 

 assume, simulating the form of a sac with a broad spread mouth opening at the side 



' See our description and illustration of this apparatus in the Contribations, Nat. Hist. N. Am. 

 of L. Agassiz, Vol. Ill, PL XP, and Vol. IV, p. 41. 



