108 JELLY-FISH, STAR-FISH, AND SEA-URCHINS 



function which is manifested by its manubrium. The 

 Medusa in question measures about one and a half 

 inches in diameter, and is provided with a manu- 

 brium of unusual proportional size, its length being 

 about five-eigjhths of an inch, and its tliickness 



Fig. 22. 



being also considerable. Now, if any part of the 

 nectocalyx be irritated, the following series of 

 phenomena takes place. Shortly after the applica- 

 tion of the stimulus, the large manubrium suddenly 

 contracts — the appearance presented being that of 

 an exceedingly rapid crouching movement. The 



