REPORT ON THE DEEP-SEA MEDUSAE. 



XIX 



can also distinguish three axes or " euthyna " in each paramere ; the longitudinal 

 axis of the paramere coincides with the central principal axis of the whole body ; the 

 sagittal axis (or " dorsoventral " axis) of the paramere is the perradius ; its lateral axis 

 (or transversal axis) lies tangentially, and touches the two adjacent parameres with its two 

 poles (" right or left pole "). 



Perrad. 



(I.O.J 



c i ,Adra.d. 

 hubrad. i m0 ) 



J fh O 1 ,Jntermd, 

 7 oubrad. Au.o.i 



Adrad. 



' (III.O.I 



PerraM 

 (io.) 



Fig. A. Zoncphyra pclagica (Diseomedusa, Ephyrida). 



Suburabral view, giving the four orders of transverse axes (with twice as many radii). The oral cross 

 (as) and the four perradial sense clubs (o 1 ) lie in the four perradii (Order I.). The gastral filaments 

 (/), the genitalia (s), and the four interradial sense clubs (o°) lie in the four interradii (Order II.). 

 The eight tentacles (to) and the tentacular coronal pouches (bt) lie in the eight adradii (Order III. ). 

 The sixteen marginal lobes (I) lie in the sixteen subradii (Order IV.). Sixteen bifurcate coronal 

 pouches, eight tentacular (6/) and eight rhopalar (ho) radiate from the central stomach (g). 



§ 29. Radial planes or meridian planes. In the Medusa?, as in all regular or symmetri- 

 cally radially constructed animals, we can distinguish a number of radial or meridian 

 planes, which have a high tectological and promorphological significance, and which are 

 defined by the position of the vertical principal axis and of one of the horizontal trans- 

 verse axes. As in all Acraspedas, and in the majority of Craspedotse, the body has the 

 fundamental form of the quadrate pyramid, we can distinguish in them four principal 



