iv PHYLUM CCELENTERATA 109 



2. THE SCYPHOZOA 



Amelia, which may be taken as an example of the 

 Scyphozoa, is one of the commonest of the larger jelly- 

 fishes, and is often found cast up on the sea-shore, where 

 it is readily recognisable by its gelatinous saucer-shaped 

 umbrella, three or four inches in diameter, having near the 

 centre four red or purple horseshoe-shaped bodies the 

 gonads lying embedded in the jelly. 



The general arrangement of the parts of the body (Fig. 

 49) is very similar to what we are already familiar with in 

 the hydrozoan jelly-fishes (Figs. 40 and 42). Most con- 

 spicuous is the concavo-convex umbrella, the convex surface 

 of which, or ex-umbrella, is uppermost in the ordinary 

 swimming position. The outline is approximately circular, 

 but is broken by eight notches, in each of which lies a pair 

 of delicate processes, the marginal lappets (mg. IpJ) with a 

 peculiar sense-organ ; between the pairs of lappets the edge 

 of the umbrella is fringed by numerous close-set marginal 

 tentacles (A). 



In the centre of the lower or sub-umbrellar surface is a 

 four-sided aperture, the mouth (mth.}, borne at the end of 

 an extremely short and inconspicuous manubrium : sur- 

 rounding it are four long delicate processes, the oral arms 

 (or. a.), situated one at each angle of the mouth and uniting 

 round it. 



At a short distance from each of the straight sides of the 

 mouth is a nearly circular aperture leading into a shallow 

 pouch, the sub-genital pit (s. g. p.), which lies immediately 

 beneath one of the conspicuously coloured gonads (gon.). 



The mouth leads by a short tube or gullet, contained 

 in the manubrium, into a spacious stomach, which 

 is produced into four wide inter-radial gastric pouches, 



