142 



A HISTORY OF FISHES 



projecting, and is traversed along its upper and lower margins 

 by a deep groove. Along each groove is a pear-shaped mass 

 of glandular tissue, the broad end of which lies towards the 

 base of the spine (Fig. 59A). There is no canal leading from the 

 gland, and it appears that the venom is set free by the rupture 

 of the cells, and, flowing down the groove, is injected into the 

 wound rather after the manner of a hypodermic syringe. It 

 may be noted here that the name Weever is believed to be 

 derived from an Anglo-Saxon word, wivere, meaning a viper. 



The Poison-fishes (Synanceidae) , belonging to the tribe of 

 Scorpion-fishes, are confined to more or less tropical seas, and 

 many of them are as ugly as they are formidable (Fig. 58B). 



B 



Fig. 59. — POISON GLANDS. 



A. Opercular spine of Greater Weever {Trachinus draco) and its poison gland. 



(After Parker); b. A dorsal spine with poison sacs of Poison-fish (Synanceia 



verrucosa). (After Giinther.) 



The glands here He under the skin at the bases of the dorsal 

 spines, each being continued into a duct situated in the deep 

 groove on either side of the spine (Fig. 59B) . Native fishermen 

 handle these fishes with great care, being well acquainted with 

 their venomous nature. It sometimes happens, however, that 

 when wading with naked feet one will step on a Poison-fish 

 lying buried in the sand : the erect dorsal fin-spines penetrate 

 the skin, and the venom is injected into the wound by the 

 pressure of the foot on the bag-Hke glands. In the PoisonToad- 

 fishes ( Thalassophryne) of tropical America the glands are even 

 more elaborate in structure, and represent the most perfect 

 organs of their kind found among fishes. Like the Weevers, the 

 spines on the gill-covers and the two spines of the first dorsal 

 fin constitute the weapons, and each of these spines is hollow 



