54 



the two oi'ders pass the one into the other, but as an ordinal type, 

 equivalent in value to either of the others, by reason of the peculiar 

 and distinctive morphology of certain of its organs. On this account, 

 Lucernaria is to be considered, and may be designated, as the cceno- 

 Ujps (xoii'og, common) of the Acalephfe. In this respect, it holds such 

 relations to the other two orders of Acalephse as do the Crinoids to 

 the other orders of Echinodermata ; or the Annelidte to the rest of 

 the Articulata ; or the Selachians to the true fishes and the reptiles ; 

 but, at the same time, containing organic features which separate 

 each of them as a type from the others. 



In order that no confusion may arise here, I would state most ex- 

 plicitly that I do not consider the Ctenophoras as one of the orders 

 of Acalephae, but deem them to be a class by themselves, equal in 

 value to either of the classes of Kadiata, whether Polypi, Acalephae, 

 or Echinodermata, and standing next in rank to the Echinodermata. 

 The division of the alimentary system of Ctenophorse into two por- 

 tions, as among Polypi, is sufficient to separate them from the Acal- 

 ephae, since the typical form of the corresponding system in the lat- 

 ter is a unity ; moreover, the position and peculiar relations of the 

 tentacles of CtenophorEe are hardly of less importance, in these con- 

 siderations, as distinctive characters. I cannot conceive that the 

 CtenophorEB may be included in the same classific type with the Acal- 

 ephae without doing violence to correlative ideas such as are ex- 

 pressed in the organism of the former ; and much less can I admit 

 that they have the most distant relation to the Polypi, excepting that, 

 like the latter, they ai'e Radiates. The same kind of arguments that 

 have been used to show that Ctenophorae and Polypi belong to one 

 class might, with equal justice, be advanced to prove that the Acale- 

 phae are Polypi. We must not mistake a similarity for an identity, 

 any more than that the cry of a child would identify it with a cat, 

 because their voices sound alike, and cannot always be distinguished 

 the one from the other by any single faculty of our senses. 



The following tabular view presents at a glance the relations of the 

 Lucernaridae to the other orders of Acalephae, and at the same time 

 indicates the position of the Ctenophorae among the other classes of 

 Radiata. 



Polypi. Acalephae. Ctenophor^. Echinodermata. 



Steganoph- 

 thalmidK. 

 Ijucemnrido! 



Gymnoph- 

 tlialmia». 



