POISON-OEGANS. 



191 



function as the caudal spines of tlie Sting-rays ; however, in 

 the Weavers the spines are deeply grooved, the groove 



^:.J: 



Fig. 99. — A dorsal spine, with 

 poison-bags, of Synanceia 

 verrucosa. Indian Ocean. 



being charged with a 

 fluid mucus. In Syn- 

 anceia the poison-organ 

 (Fig. 99,) is still more „. mr. r> , . r^i t, • 



o '' lig. 100. — Opercular part of the Poison-apparatns 



developed : each dorsal of Thalassoplmjnc (Panama). 



spine is in its terminal ^- Hinder half of the head, with the venom-sac* 



•11 • 1 *'*' ^ii'^- O"! Lateral line and its branches ; 



halt provided with a ^^ Om-opening ; c, Ventral fin ; d. Base of 



deep groove on each Pectoral fin ; e. Base of dorsal. 



. , , , T 1 1 f> 2. Operculum with the perforated spine. 



Side, at the lower end oi 



which lies a pear-shaped bag containing the milky poison ; 

 it is prolonged into a membranous duct, lying in the groove 

 of the spine, and open at its point. The native fishermen, well 

 acquainted with the dangerous nature of these fishes, care- 

 fully avoid handling them ; but it often happens that persons 

 wading with naked feet in the sea, step upon the fish, which 

 generally lies hidden in the sand. One or more of the erected 

 spines penetrate the skin, and the poison is injected into the 

 wound by the pressure of the foot on the poison-bags. Death 

 has not rarely been the result. 



