THE ETDBA AND JMLLT-FI8H. 



29 



Fig. 24— The I)olyp ot Co- 

 ryne mirabilis^ with a 

 medusa-bud at a. (Much 

 enlarged.) 



masses on the reefs of Florida and the Pacific Ocean. The 



name is derived from the numberless 



minute holes or pores scattered OTcr the 



surface in which the nutritive (Fig. 33, 



a) and tentaculated zooids (Pig. 23, b) 



live. On breaking off pieces of the living 



coral one's hand is stung and made sore 



for days by the stings from the lasso-cells 



(Fig. 23, c, d, e), so poisonous is this 



coral-like growth. 

 A common Hydroid on our northern 

 shores is the Cory^ie 

 (Fig. 24), which differs 

 from the foregoing kinds 

 in producing a free bell- 

 like form called a me- 

 dusa, or jelly-fish (Fig. 25). Most jelly-fishes 

 are more or less bell or umbrella-shaped, and 

 are delicate transparent creatures which move 

 about in the water, by opening and closing 

 the edge of the disk-like body. From the 

 centre of the body hangs down a hollow pro- 

 boscis-like tube, the stomach, from the base 

 of which radiate four canals or passages which 

 open into a circular passage around the edge 

 of the disk. This is the water-vascular 

 system, and the fluid it contains is sea- 

 water mixed with the digestive fluid; this 

 fluid thus rudely corresponds to the blood of 

 higher animals. Four long thread-like ten- 

 tacles in the Coryne hang down from the 

 edge of the disk. These delicate jelly-fishes 

 possess a nervous ring passing around the 

 edge of the disk, and also eyes and usually 

 ears situated at intervals on the edge of the 

 the first timO a true nervous 



Fia. 35.— Free Me- 

 dusa of Coryne, 

 with the four 

 ~ong tentacles. 

 (Enlarged ) 



disk. We thus find for 

 Bystem. 



