300 



THE AMERICAN NATURALIST [Vol. XLI 



was squirted from the spiracle with such energy as to rise through 

 an inch of water and some seven or eight inches vertically upward 

 into the air. Frequently the stimulation was followed, not only 

 by the spouting, but by a sudden dash to another part of the tank, 

 as if to get away from the annoyance. 



Tactile stimulation of the skin in the region of the eye also 

 usually caused spouting. A gentle touch uj^oii the outer corneal 

 surface of the eyeball almost invariably provoked a particularly 

 vigorous spouting from the corresponding .s))ira( le. Indeed, stinni- 

 lation of the cornea w^as found to be a more certain way of ]>r()- 

 voking spouting than stimulation of the spiracle itself. The 

 response was always immediate and definite and ui nearly every 

 instance unilateral. 



I tried also the introduction of solid materials of one sort and 

 another into the gill chambers. I first tried sand, allowing a little 

 to sift into the spiracle when it opened for an inspiration. Some- 

 times a spouting resulted, but equally often, even though a con- 

 siderable quantity of sand was introduced, no response whatever 

 followed. 



P^xperimenting in a similar way with another fish, T found in the 

 aqiiarimn some shre<ls of filmy substance of doul>tful nature. 

 Tlu-v appeared like hits of slou-he.l-otf .kin. It well exemplllies 

 the impiompni < 1, u .< in ..t dl -.1 di. m (\punnuus ilial, makino- 



hand, I caused some of this doubtful filmy substance to he sucked 

 into the spiracle at an inspiration, invariably material of this 

 sort was promptly expelled by spouting. Often one or two in- 

 spirations intervened between the one by which the foreiun material 

 w^as drawn in and the spouting by w^hich it was expelled. I sually 

 the spouting occurred from both spiracles at once,— rai-ely from 

 only the one at which the foreign material was introduced. The 

 material was always ejected by the same sjiiracle at which it 

 entered. 



In the one-sided spouting the action of the unstinuilated spiracle 

 appeared to be uninterrupted. The stinnilated spiracle simply 

 remained open during one closing of the other. 



Summarizing the foregoing accoutu, it apj)ears that the spiracle 

 of the common skate serves chiefly as an in-take for the respiratory 



