THE ADULT AURELIA. 71 



forewarn you that the proportions of the youngest Ephyra are 

 not retained throughout life, but that they are constantly and 

 gradually changing, from the fact that some organs grow faster 

 than others. Starting from the central cavity (m), which is here 

 seen through the thickness of the disc, there are, in the first 

 place, four channels (ch) which pass in four different directions, 

 opposite the corners of the proboscis, straight to the edge of the 

 disc; secondly, there are four other less prominent openings, 

 alternating with the outlets into the four channels just mentioned, 

 which lead into these four very broad three-sided cavities, (re, re 1 , 

 re 2 ,) that occupy nearly the whole area about the central diges- 

 tive chamber. These last are especially devoted to the office of 

 enclosing the reproductive organs, which lie in the form of a 

 deeply plaited ruffle (r, r 1 ) along the margin of each cavity, 

 and at the same time they allow the passage of the fluids from the 

 centre toward the periphery of the disc, by means of several chan- 

 nels, of which there are, for each cavity, three principal ones, (t, t l , 

 2 ,) which go nearly direct to the marginal canal (t~) of the disc, 

 and three or four others, which form a net-work of tubes. These 

 last are developed between the sixteen broad channels which 

 appeared in the youngest Ephyra, and which are here repre- 

 sented by the same number of narrow straight tubes, (ch, t, t 1 , t 2 , 

 &c.,) going alternately to the eight eyes (o) and to the middle 

 (t, t 2 , t*, t 6 ) of the eight intervening groups of tentacles. Between 

 the straight and the branching canals there is more or less of lat- 

 eral communication, (an,') but not, however, until late in the life 

 of the animal, at which period this figure was drawn. 



The broad circular channel of the Ephyra is here a thin tube 



between the principal canals and the branching ones; re, re 1 , re 2 , the four tri- 

 angular cavities opening on the one side into the central cavity (m), and on the 

 other side into the canals of the second, third, and fourth sets ; r r 1 , the frilled, 

 ribbon-shaped reproductive organs lying, along the margin of the triangular cavi- 

 ties, in the distance, i. e. nearest the oral face ; at, the opening leading to an 

 excavation on the oral face and immediately opposite and nearly coextensive 

 with each triangular cavity ; o, the eye, bordered by the ocular lappets (/) ; 

 v, the veil thrown outwards at the moment when the umbrella begins to contract. 

 Original. 



