JELLY-FISHES. 



109 



greatest difficulty taken from tlie water without breaking. Its motion through the 

 water is a graceful undulation to which body contractions and vibrations of the combs 

 contribute. 



The mouth of Cestus is situated midway in its length between the two extremities 

 of the belt-like body. On either side of it there hangs a single short tentacle which 

 protrudes from a tentacular sac. Opposite the mouth there is a sense-body, or otocyst 

 as it is commonly called, in which is situated a compound otolith. The rows of combs 

 upon the external surface of the body of Cestus are not as conspicuous as in some 

 other genera, but the course of their lines can be easily traced. The enormous expan- 

 sion of the two lateral lobes of the body which give a girdle-like form, impart to the 

 rows of combs which lie in these regions an extraordinary development as compared with 



Fig, 103. — Cestus veneris, Venus girdle. 



those which lie in the intermediate regions or on the flattened sides of the body. The 

 adult Cestus reaches a length of from two to three feet, and is one of the largest as 

 well as most beautiful ctenophores of the Mediterranean. There is scarcely any color 

 in its body walls. 



Of the many genera of medusa3 closely or remotely allied to Cestus, one of the 

 most interesting and least known is a genus called Ocyroe from the Gulf of Mexico 

 and the Caribbean Sea. This genus, like many other ctenophores, and especially like 

 Cestus, is very transparent, and has on the external body-surface, eight rows of vibra- 

 tile combs, the lines of which converge at a point near that pole of the animal in which 

 a sense-organ is situated. One of the most extraordinary things about Ocyroe is the 

 great development of' two opposite sides of the body into wings. In Cestus the oppo- 

 site sides of the body are so developed that a band or belt-like form is given to the 



