148 HALF AN HOUR WITH SEA-MATS AND SQUIRTS. 



Fig. 78. 



shown in Fig. 78, where the position of the spines 

 or bristly hairs is also given. 



We now come to another division of the 

 Molluscoidea, common in British seas, and some of 

 the members of which our readers cannot fail to be 

 introduced to in the course of their seaside rambles. 

 This division is called Tunicata, on account of the 

 bodies of some of the animals being enveloped 



in a leathery integument, 

 which is called a "test," 

 and takes the place of the 

 ordinary shells of a bivalve. 

 Inside this is another mem- 

 brane, which possesses a 

 muscular power of con- 

 tracting, and, in doing so, 

 can squirt or force out 

 the sea-water. Hence the 

 popular name of " sea- 

 squirts " is given to these 

 animals. They are found 

 solitarily inhabiting a 

 stone or a rock, in twos 



Meiribranipora pilosa, x 60. 



and threes, and also in colonies. Many of them are so 

 like the sewn wine-skins still in usejn eastern coun- 

 tries for bottles, that they go by the term Aseidians 

 (from " askos," a wine-skin). The two openings stick 

 out, and cause the resemblance to be very striking. 

 Like the Polyzoan animals just mentioned, the Asei- 

 dians have the mouth opening into a respiratory cham- 



