164 lOPULAR HISTORY OV THE AQUArdUM. 



depressions, called ambiihcra, because they are pierced with 

 rows of holes through which are ]3ut forth sucker-tubes, 

 lilce those of Star-fishes and Sea-Cacunibers_, supposed to be 

 more or less used in locomotion. These animals have a 

 mouth and a vent : the former below, and the latter in va- 

 riable positions. Whatever relative positions these two open- 

 ings take, the intestinal canal leading from one to the other 

 is winding, aiid is attached to the inside of the sliellj case by 

 means of what is called an integument, as well as all the 

 internal lining, with vibratile cilia, and which is connected 

 with the function of respiration. They are believed to 

 possess also a muscular apparatus, which has pulsations, and 

 branching veins connected with it, like the heart in more 

 advanced animals. They are also asserted to possess a 

 nervous system like that of tlie Holothuriada. 



Means of Vrogression. 



The TlclnniclcR use both suckers and spines for locomo- 

 tion. Of course only those on the under, or oral side, or 

 near the base, can be used in this way. To those on the 

 base and upper part of the sides some other functions must 

 be assigned, and it is well known that one organ is often 

 applied to several uses, as well as several different organs to 



