174 



CTENOPHORxE. 



Part II. 



SECTION II. 



SUBDIVISIONS or CTEXOPIIOR.E, FORMING SUBORDERS. 



A comj^ai'ison of the various attempts to subdivide the Ctenophora^ is very 

 instructive Avith reference to the principles upon Avhich chissifications may Ijc leased. 

 Esehscholtz,^ as early as the j-ear 18-9, divided them into three families: Calli- 

 ANiRiD.E, with the genera Cestuni, Cydippe, and Callianira ; Mnemiid.e, with the genera 

 Eucharis, Mnemia, Calymma, and Axiotima; and Beroid.e, with the genera Beroe, 

 Medea, and Pandora. Mertens admits four families : Cestums, Callianiras, Beroes, 

 and Idyas. Lesson, who considers the whole order as a family under the name 

 of Beroide.e, subdivides them into eight tribes : CcstoiJcw, with the genera Cestum 

 and Lenniiscus ; Calliauinc, with the genera Callianira, Chiaia, Polyptera, Mnemia, 

 Bucephalon, and Bolina ; Leucothoew, with the single genus Leucothoea ; Calijmmece, 

 with the genera Calymma, Eucharis, Alcinoe, LeSueuria, and Axiotima ; Neimlw, 

 with the genus Neis ; Oci/rocw, with the genus Ocyroe ; Q/dijipw, with the genera 

 Mertensia, Anais, Eschscholtzia, Janira, and Cydippe ; and the Bcrocv proper, with 

 the genera Beroe, Idya, Medea, Cydalisia, and Pandora : to which, strange to say, a 

 number (jf Diphyida\, Tunicata, Noctiluca, and Bipinnaria, are added. Leuckart, who 

 considers them as a distinct class, suljdivides them primarily into two orders, the 

 Eurystomata and Stenostomata. Gegenbaur admits iive families, which he groujjs 

 inider three heads : 1°, those the body of which is extended into lolies. with or 

 without tentacles, the CaUiuniriJtc and Cah/mnidw ; 2"", those which have no lobes, 



^ Whrn considering the works of a master in 

 any department of Natural History, I am in the 

 habit, first, of identifying myself with liis views as 

 completely as I possibly can, and ascertaininiz; how 

 far, in the course of the progress of our science, 

 addition.nl evidence may have been accumulated in 

 support of his opinions, even if the new facts should 

 tend at the same time to modify them ; fur it 

 is generally the case, that those who have bern 

 long engaged upon a difficult subject instinctively 

 perceive relations which become more apjiarent 

 only witli the lapse of time. Next, I [iroceed to 

 a critical revision of tiic bearing of each fact, in 

 order to avoid one-sided ajipreciatious and useless 



discussions. And, finally, I present the result of 

 my own investigations, combined with the information 

 thus obtained from the labors of my i)redecessors. 

 Tliis method I have found particularly useful in 

 tlie study of the Acalephs, must of which are de- 

 scribed in so \\vM\j different ways by <liflerent 

 authors and at different j^eriods, witii siu-h unequal 

 knowledge of their structure, that, unless we supjjly 

 the dcticicncies of older writers by tlie light cast 

 upon tlicse animals from modern investigations, a 

 large luunber of tlie most inten'sting types of the 

 class would Iiave to be entirely left out of con- 

 sideration in our I'enewed attemjits at tracing their 

 natural alliuities. 



