Chap. I. STRUCTURAL FEATURES. 165 



jjapillosa of Delle Chiaje. The close connection which exists between the rows of 

 locomotive flajjpers and the chymiferous tubes is so similar to the general organi- 

 zation of the ambulacral system of the Echinoderms, that I do not hesitate to 

 consider these structures as homologous.^ 



The sexual organs of the CtenophorjB are closely connected with the chymiferous 

 tubes, as in all Acalephs, and, indeed, in all Radiates ; for they bear the same 

 homological relations to the radiating chambers of the Polyps, as they do to the 

 ambulacral system of the Echinoderms. In Ctenophoraj the ovaries and spermaries 

 occupy small pouches upon the sides of the ambulacral chymiferous tubes: sperm- 

 aries and ovaries existing in all individuals, and alternating witli one another in 

 such a manner, that, while each chymiferous tube has sjiermaries on one side and 

 ovaries on the other, the proximate sides of adjoining tubes have the same kind 

 of sexual organs, that is, either spermaries or ovaries, and, alternate intervals between 

 adjoining tuljes, different kinds of organs. The mode of reproduction of the Cte- 

 nophorai has been traced recently by Semper and McCrady ; and fragments relating 

 to the same subject have also been contributed by Vogt, Kolliker, J. Miiller, and 

 Gegenbaur. Since the publication of my paper upon Beroid Meduste, I have had 

 an opportunity myself of studying the entire development of Pleurobrachia, an 

 account of which will be given in the sequel. They vmdergo a direct transfor- 

 mation, and the young very early acquire the characters of the adults. 



From this general sketch of the Ctenophorie, it may already be inferred that 

 they constitute a very natural group among Acalephs, entirely distinct from the 

 Discophoraj and from the Hydroids, and unquestionably occupying, as an order, 

 the highest position in the class, if the degrees of complication of strictly homo- 

 logical structures are at all characteristic of orders and may determine their relative 

 standing. Since Goldfuss first recognized the natural limits of this group of 

 Acalephs, and Eschscholtz, with his usual precision and accuracy, characterized it 

 as a distinct order, all naturalists have acknowledged the propriety of combining 

 these animals into one and the same division; though some have considered them 

 simply as a natural family, while others have raised them to the rank of a class. 

 As I have already stated, I believe them to be an order of the class of Acalephs, 

 and shall hold them to be nothing more and nothing less than an ordei', so long 

 as there is a possibility of distinguishing families, orders, and classes upon definite 



* Of course, in following up this homology it Asterioids ; for it is very simple in the Synaptoids 



must be remembered that the ambulacral system among the Holothurians, even more so than in some 



of the Echinoderms is not so complicated in all Ctenophora;, as, for instance, in Bolina. But of 



of them, as it is, for instance, in the Spatangoids this, and of the special homologies of the chy- 



and Clypeastroids, or even in the Echinoids and miferous tubes, more presentlj'. 



