JELLY-FISHES. 109 



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

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

 contribute. 



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

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

 jji'otrudes from a tentacular sac. OpjDOsite 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 

 otlier 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 



tliose which lie in the intermediate regions or on tlie flattened sides of the body. Tlie 

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

 well as most beautiful ctenophores of the INIediterranean. There is scarct'ly any color 

 in its body walls. 



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

 most interesting and least known is a genus called Oci/roe 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 

 :i sense-organ is situated. One of the most extraordinary things about Oci/roe is the 

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

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



