108 MANUAL OF ZOOLOGY sect. 



however, from those we have hitherto met with, in having 

 no circlet of tentacles round the mouth, but a single, long, 

 branched tentacle (/) arising from its proximal end, and 

 bearing numerous groups or " batteries " of stinging-capsules 

 {ntc). Others are dactylozooids or feelers (dz) — mouth- 

 less polypes, each with an unbranched tentacle springing 

 from its base. Near the bases of the polypes and dactylo- 

 zooids spring groups of sporosacs (B, s, s 1 ), some male, 

 others female ; and finally delicate, leaf-like transparent 

 bodies — the bracts or hydrophyllia {hph) — partly cover the 

 sporosacs. Halistemma occurs in the Atlantic and Mediter- 

 ranean. A closely related form (Agalmopsis cava) occurs 

 off the coast of New England. 



2. THE SCYPHOZOA 



Aurelia, which may be taken as an example of the 

 Scyphozoa, is the most common of our larger jellyfishes, 

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

 readily recognisable by its gelatinous saucer-shaped umbrella, 

 from eight to twelve, and sometimes fifteen inches in diam- 

 eter, 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. 

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

 the hydrozoan jellyfishes (Figs. 41 and 43). Most con- 

 spicuous is the concavo-convex umbrella, the convex sur- 

 face 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. Ip) with a 

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



