HYDROZOA. 
57 
larger and commoner kinds of Jelly-Fish or Sea-Nettles. A brief 
account is given below of Aurelia aurita* (Model and specimens 
in Case 3), whose phantom disks are so often seen in summer 
time slowly swimming below the surface. In the centre of the 
shallow umbrella are four purple horseshoe-shaped or circular 
generative masses ; in the centre of the under surface is the 
manubrium prolonged into four arms ; the margin of the umbrella 
is provided with a fringe of very short fine tentacles, the uniformity 
Fig. 20. 
Carmarina hastata, one of the Trachomedusx. (After Haeckel, and from Encyc. 
Britannica.) 
of the fringe being broken by eight notches, each containing 
a tentaculo-cyst ; each of the latter (Fig. 21) is covered by a 
pair of minute lappets, hence Medusae of this type were called 
Covered-Eyed ; while those of the Hydromedusan type, being 
without lappets, were called Naked-Eyed. 
The thickness of the umbrella is traversed by a system of simple 
and branched canals, which pass from the central stomach to a 
circular canal running round the margin of the umbrella. Pro- 
Case 3, 
Upright part. 
Case 3, 
Upright part. 
