32 
Tank No. 1. 
Echinus lividus and allied forms are eaten in the fish-market raw as 
we eat oysters. Sphaerechinus (Fig. 36) is of a beautiful violet or red¬ 
dish-brown colour; and Doroeidaris (Fig. 42) is remarkable on account 
of the size and thickness of its spines, which are few in number. 
The Sea-cucumbers are very common in the Bay of Naples, and the 
Aquarium contains about half 
a dozen kinds; among others 
the brown Holothuria tubu- 
losa (Fig. 39), attaining the 
length of one foot; and Sticho- 
pus (Fig. 46), which is not 
round but flattened. Both of 
these are very remarkable for 
containing frequently within 
their body a fish, Eierasfer 
acus, 8 to 10 inches long, 
which at times may be seen 
Fig. 43. Luidia fragilis, |/ 4 nat. size. protruding its head from the 
anus of its host. It feeds on 
Fig. 46. Stichopus regalis, V 2 nat. size. 
