CHAPTER SECOND 



THE NATURAL FAMILIES OF THE CTENOPHOR^. 



SECTION I. 



FAMILY CHARACTERS IN GENERAL AMONG CTEXOPIIOR^. 



Since it is probable that hereafter the natural families of animals may be 

 characterized by a distinct category of structural features, and with greater pre- 

 cision than before, in accordance with suggestions I have already made in the 

 first volume of this work (p. 155), I will only add here a few remarks upon the 

 manner in which I conceive that this should be done in the class of Acalephs. 

 The characteristics of the families require a thorough revision throughout the 

 animal kingdom ; for, of late, it has been customary among naturalists simply to 

 select some prominent genus among those which appeared closely related, and, giving 

 its name a patronymic termination, to call family almost any kind of combination 

 of genera associated under such a head, sometimes even without assigning to such 

 would-be families any characters at all. There are many hundred families now 

 recorded in descriptive works of Zoology which have no better foundation than 

 this, and a great many more to which characters are assigned in no way bearing 

 upon the features upon which natural flxmilies may be founded. This state of 

 things should no longer be tolei-ated ; or, at least, if such loose proceedings cannot 

 be prevented in our science, they should no longer be received as contributions 

 to its advancement. It is one thing to give a family name to an arbitrary associ- 

 ation of animals, and quite another thing to investigate the structural features 

 upon which a family may be founded. If the essential character of a family 

 consists in the typical form of its representatives, it becomes a scientific problem 

 in Zoology to ascertain what are the structural features which determine their 

 peculiar pattern ; and I hold, that, to characterize a natural family correctly, it is 



