122 ACALEPIIS IN GENERAL. Part I. 



partite structure of the Rugosa is an acalephian feature, nowhere observed among 

 true Polyps, but characteristic of Lucernaria, which is a genuine Hjdroid Acaleph. 

 I may also allude to a more remote argument for referring the Rugosa to the 

 Acalephs. There are simple ones among them, and others forming rather loose 

 communities, composed of comparatively few individuals ; but, whether simple or 

 combined, each individual of this type, with its successive floors, presents a striking 

 resemblance to a Strobila. Rugosa, indeed, may be considered as a prototy^ie of 

 the Acalephs, combining the most characteristic embryonic features of the class 

 with the simplicity and peculiarity of structure of its lowest type. 



When considering the different orders of Acalej^hs singly, I shall show that their 

 flxmilies are founded upon different patterns of form, their genera upon ultimate 

 structural details, and their species upon the proportions of their parts, and the 

 relations of individuals to one another and to the surrounding mediums. To 

 introduce these topics here, would involve me in an amount of details, which are 

 best referred to the special parts of this monograph. 



Although an order in Zoology esjiecially signifies the relative rank of the 

 members of a class, as exhibited in the complication of their structure, it is not 

 in the orders alone that we recognize different degi-ees and different kinds of 

 superiority or inferiority. As I have already stated elsewhere (vol. 1, j). 152), 

 groups of a more or less comprehensive value may exhibit a relative superiority 

 or inferiority ; nor is an order a natural group that has no other meaning but 

 that which it derives from its higher or lower position. Tlie primary branches 

 of the animal kingdom do not all stand on a level : Radiates, as such, are im- 

 questionably inferior to Mollusks or Articulates or Vertebrates, even though some 

 Radiates may have a more highly complicated organization than some of the lowest 

 Fishes. We assign to the Radiates a lower position than that of the other l^ranches, 

 because the elements of their plan of structure are of an inferior stamp ; and we 

 place the Vertebrates highest, because the ]Aan of their structiu'e is in itself the 

 most complicated : but it would be difficult to weigh the different organic tendencies 

 combined in either the Mollusks or Articulates so nicely as to prove that either 

 of them is su^jerior to the other, though, unquestionably, as primary divisions of 

 the animal kingdom, they are superior to the Radiates and inferior to the Verte- 

 brates. The idea of placing either the Mollusks or the Articulates immediately 

 above the Radiates, so as to establish a gradual transition between them and the 

 Vertebrates, seems entirely out of the question, since the most distinguished natu- 

 ralists who have attempted to arrange the first primary divisions of the animal 

 kingdom in a series have failed to produce convincing argimients in fixvor of the 

 superiority of the Mollusks over the Articulates, or of the latter over the former. 

 The fact is, there is quite as high authority for one as for the other position 



