72 



Animal Life by the Sea-shore. 



certain times of the year, however, they are very abundant on 

 the surface of the sea, and can be collected in enormous 

 quantities bj' means of a fine net. Although varying in shape, 

 jelly-fishes are pretty constant in structure. The main organ, 

 bell-shaped or saucer-shaped, and of great transparency, is 

 usually referred to as the " bell " ; by the pulsation of this 

 bell locomotion is effected. From the centre of the under- 



surlace is given off a 

 little stomach - tube, 

 carrj'ing the mouth 

 at its extremity, the 

 latter leading into a 

 central caxdty from 

 which a number of fine 

 canals lead to the more 

 outlying parts of the 

 body. The edge of 

 the bell is proxaded 

 \vith a varying number 

 of tentacles, which, 

 like those of a polyp, 

 carrjr a stinging ap- 

 paratus, used both for 

 the capture of food 

 and for defence. The 

 large Jelly-fishes which 

 often attract the 

 attention of visitors 

 to the seaside, usually 

 found as inanimate 

 lumps of jelly left 

 behmd by a receding 

 tide, are of a similar 

 nature, but show a 

 greater complexity in 

 their structure. Like 

 the smaller forms, they 

 usually have a polyp stage in their life-history, although it is 

 frequently much reduced. Only a few forms are at all 

 abundant on our coasts. The commonest is undoubtedly 

 Aurelia auriia, easily recognised by its flat, saucer-shaped bell, 

 the margin of which is fringed with innumerable small 

 tentacles. The mouth of this, as well as most other species, 

 is produced at the corners into four large lips. Aurelia reaches 



V V 



inc. 



5. RHIZOSTOMA PULMO. 



