196 CTEXOrnOR-E. Taut II. 



risrlit track Avhon ho boiran to sulnlivide the Cydippiiliv into two ilistinot groups. 

 and lie w;u< onlv prevomod iVoiu carrying out his suggestion to its k'gitiniato Huiits 

 by insufficient materials. Taking the rounded lonns ot" Cydippidtv a-s the repre- 

 :«eutatives of the huiited family of that name, and the compressed ones as the 

 representatives of another family, for -which I woidd propose the name of Mer- 

 iensida\ \ve may now proceed to a comparative survey of the distinguishing 

 characters of the two. 



The CrPiPPiP.E proper are remarkable for the striking similarity of their eight 

 spheixnneres. There is so little dilierence between them, that though I have been 

 lamiliar with one representative of this group for a great many years, and though I 

 have kept hundreds alive annually for weeks in succession, it was not until recently 

 that I perceived how. under this seemingly perfect radiation, the same antitropy 

 of the spheromeres may l^e recognized which characterizes the most compressed 

 f\"j)e.s of Ctonophonv. in which bilateral symmetry is most prominent. Here, then, 

 as! in all Ctenophoiiv. there are an anterior and a posterior pair of spheromeres 

 and two latei-al pail's, and the direction of the circumscribed area and of the 

 actiuostome marks the direction of a plane which may divide the body into equitl 

 lateral halves : ;md Bere, as in all the Ctenophoinv. the cadiac and the tentacular 

 chATuileixius tubes trend in another plane, at right angles with the preceding. Theii- 

 apparent equality, however, and their symmetrical radiation, combined with the 

 presence of two lateral tentacles protruding in the direction of the abactinal pole, 

 constitute the most striking character of the family, to which the following genera 

 belong: Pleurobrachia Fhvi. (^Cydippe Fich.). Janira Oh,!. Eschscholtzia Less., and 

 Merteusia Gojcub.. for which I would substitute the name Dryodora. since Lesson's 

 irenus Mertensia must be retained. To these I would add the genus Hormiphora 

 for Gegenbaiu-"s Cyilippe hormiphora. Lesson's genus Anais^ must be suppressed. 

 Gegenbaiu- erroneously refers the genus Oc^^■oe Biiiu/ to the lamily of the Cydippi- 

 da^ : it belouirs to the Ctenophoi-a? Lobata>. 



3lEKTE.\sir>.E. A very ostensible character of this family consists in the llatness 

 of the sides of its representatives. But this is a more apparent than real pecu- 

 liaritv : for in ;uiim;ils. whose spherosome is extensively movable in every direction. 

 a sliirht lateral compression vanishes from sight whenever the body is greatly 

 expanded or contracted. Yet the structtu-al combiuation which deternunes that 

 flatness is not only a permanent, but also a very striking, characteristic, readily 



^ It ij with deep regret that I feel eonipelled jo leph. described Iw S;ir# as Cyilippe qaadrioostaia, 



lav the unspariiii: hand of criticism upon a monu- and probably the immature state of his Mneniia 



ment of parental afleetion erected by Lesfon to a norvegica. as McCrady suggested, after tracing the 



beloved child : but the genus Aiiais cannot stand embryonic growth of his Bolina littonilis. He .also 



in our science. It is founded upon a young Aca- regitrds Will's Cydippe brevicostata as immature. 



