LUCERNARI.E AND THEIR ALLIES. 9 



two diagonally opposite, dorsal and ventral corners of the four-sided proboscis, 

 so that two other corners and two pair of reprodiuti\e organs, as well as two 

 partitions, stand respectively on the right and on the left.^ 



CHAPTEE. III. 



ANTERO-POSTERIOR (C E P II A LO - C A U D A L) REPETITION. 



§ 4. Th'i Scypliostoma and Epliyra, varieties of the same moqJi. 



20. It would seem to be incumbent on us now to proceed at once to define 

 more precisely tlie morphological and individualistic character of the Lucernarise ; 

 but before we do that it seems desirable, in fact necessary, to prepare the way 

 more clearly by a specific statement of our views in regard to the organization of 

 the strobiloid Acalephre, and particularly in reference to their morphology. If all 

 the members of this order originated and developed in the same way as a certain 

 Pelagia was observed to do by Krohn,- there woidd be neither such a thing as a 

 strobiloid Acaleph, nor any dispute as to the strict individuality of the medusiform 

 Acaleph ; but reproduction by that method is not the only one, in fiict it is an 

 extreme betAveen which and the more commonly known process there are no 

 graduated means, such as exist so notably among the Hydromeduste. In this Pelagia 

 the scyphostoma and the ephyra are merged into one ; or perhaps rather — and we 

 only suggest the thought — the whole scyphostoma is developed from an early 

 period directly into the ephyra, instead of first taking on a certain and quite 

 advanced degree of complexity, and then metamorphosing itself, by self-division in 

 part, into another variety of the same morph. It is in the latter case, i. e. strohi- 

 lism, that we meet with a form of repetitive partition almost unknown among the 

 Hydromcdusa? ; indeed we believe only to be found in the moniliform group of 

 medusoids of Eudendrium, strung end to end. 



21. In all probability the cephalic members of most of the Ilydromcdusse are 

 derived from the hilaferal element of polarity, but in the strobiloid AcalrpluB it 

 would seem to be quite clear that antero-postrriorltij exhibits its peculiarity by an 

 indeterminate number of cej^Iiahycaudal repetitions along the longitudinal axis. 

 We do not propose to enter here into any detailed argument to prove this, but 

 will simply refer to the chapter (Part XI) on individuality for the minutia% and 

 merely state the facts which lead us to this conclusion, without further comment. 



' See the section on the " Criterion of Symmetry," in Part XY, for proofs of the correctness of the 

 above view in regard to the ]iosition of the dividina: jilane. 



' See Krohn, " Uebcr die fruhestcu Eutwickl. der Pehigia noctiluca," Miili. Archiv, 185r>, p. 491, 

 Taf. XIX. 



2 February, 1877. 



