590 TELEOSTED CHAP. 
poisonous property of the dermal secretion of the Fish. Cope 
believed an orifice at or above the axil of the pectoral fin in 
Noturus to be the opening of the duct of a poison-gland ; “from 
it may frequently be drawn a solid gelatinous style ending in a 
tripod, each limb of which is dichotomously divided into short 
branches of regular length.’ I think this condition of things 
has nothing to do with a poison-organ, and is merely a repetition 
of what is observed in Loaches and in the Characinid Yeno- 
charax, Where I have found a gelatinous substance filling the 
short duct by which the membrane of the air-bladder is placed 
in communication with the skin and the sensory organ of the 
lateral line. Most Silurids can live in very foul water, taking in 
air from the surface, and spend a comparatively long time out of 
the water, without being possessed of any special apparatus for 
atmospheric respiration. A few genera, however, are provided 
Fic. 356.—Harmout, Clarias anguillaris (after Valenciennes). 4 nat. size. 
with an accessory breathing organ: in Clarias, Heterobranchus, and 
allies, there is a dendritic superbranchial organ, in Saccobranchus 
a long air-sac, extending from the first branchial cleft along the 
side of the body, as described above, p. 295; and these Fish can 
live for days on land.  Clarias lazera has been observed, in Sene- 
gambia, to spend several months of the dry season in burrows, 
from which it emerges at night to crawl about in search of food. 
Many Silurids, but especially Doras and Synodontis, are known 
to produce sounds in and out of the water by means of a special 
mechanism of the air-bladder and the processes of the vertebrae 
above it, combined with the movements of the pectoral spine 
grinding in the glenoid cavity.’ In South America, Doras has been 
observed to move rapidly on land, projecting itself forward on the 
pectoral spines by the elastic spring of the tail, travelling long 
journeys over land, from one drying pond to another, spending 
whole nights on the way ; these migrations sometimes take place 
1 Cf. Sérensen, C. R. Ac. Sci. Ixxxviii. 1879, p. 1042, and ‘‘ Lydorgane hos Fiske ” 
(Copenhagen, 1884) ; Bridge and Haddon, P.R.S. lv. 1894, p. 439. 
