242 



ZOOLOGY 



of these are provided with glands which open to the exterior 

 near the tip of the jaws ; the glands are said to secrete a sticky 

 fluid by means of which the Echinoid attaches to itself pieces 

 of seaweed, etc., which screen it from observation. The smaller 



Fig. 144. — Pedicellariae of Echimus saxatilis. 

 After Gegenbaur. 



a. Open. b. Closed, 



pedicellariae serve chiefly to clean the surface of the body, and 

 some of them serve as locomotor organs, and to catch passing 

 worms, etc. They are well supplied with nerves, and some of 

 them have in addition a special tactile organ. 



The peristomial area immediately surrounding the mouth 



Pig. 145. — View of Sea Urchin, witli part of the shell removed to show the course 

 of the alimentary canal (from Leuckart). After Cuvier. 



1. Mouth, surrounded by five teeth (dis- 5. The siphon. 



placed). 

 Lantern of Aristotle. 

 Oesophagus, coiled 



rectum. 

 Ovaries with oviducts. 



6. Oral vascular ring. 



7. Aboral sinus. 



intestine, and 8. Blood-vessel accompanying intestine. 



9. Ampullae at base of tube-feet. 



