No. 485] THE FUNCTIONS OF THE SPIRACLE 301 



stream, but at somewhat regular intervals the stream is reversed 

 and an expiration takes place via the spiracle, which thereby 

 becomes a spout-hole. With quickened respiration due to exer- 

 cise, the spouting occurs much more frequently than in the resting 

 fish. Also, when a skate is confined in a small volume of water 

 which is not changed, respiration is quickened and spouting occurs 

 much oftener than under normal resting conditions. Wliether 

 in this case the higher rate of resj)ii'ati()n is due dircctlv to the con- 

 dition of the water, or to the activily vaumhI l)y tiie unfavorable 

 quality of the water, I am unable to say. :\rKtMidi ick (7'.t ) states 

 that, in the presence of an insufficient supply of oxygen tlie fish 

 "breathes hurriedly." Finally, spouting occurs with t'X(•e»!^c 

 frequency in skates which are just beginning to recover fioni an 

 advanced stage of asphyxiation. What, in view of these fatts, 

 is the probable r6le of the spouting, so far as it is a resj)irat()i v act ? 

 May it not be roughly analogous to " taking a deep bn atli r An 

 occasional reversal of the respiratory stream may sei\t' to < !ear 

 out the gill chambers, resulting in a more nearly complete ehanue 

 of water in them. The ureater frequency of the sjxiniinL;- when 

 respiration is (luiekentMl. by whatever cause, and its exce^sivt^ 

 frequency in recovery from asi)hyxia indicate, I tliink. thai it has 

 some importance in the way of increasing the ellicitMuy of the 

 respiratory process. 



Spouting in response to tactile stinuiiation in ihe vicinity of the 

 spiracle indicates that the fish may, uiKh-r natural comhtions. em- 

 ploy the spout-hole as a means of expelHiiL;' foi'eiuii soHd materials 

 from the gill chambers, or of dislodging objects from the surface 

 of the body in the region of the spiraeh^s and (>yes. The bt^havior 



the sea-bottom havt> a habit of settling lh(Mn>elves into the sand 



apparently, be very likely to sift into the spiracles, and one might 

 suppose that sand would be particularly irritating. Hut in my 

 experiments the skates were indill'eriMU to the introduction of con- 

 siderable quantities of sand, while soft iilmy materials were 

 promptly spouted out. On fiu-ther consideraiion. it occurred to 

 me that sand, being a finely divi(le<l substance, would easily wa>li 

 out through the gill clefts, whereas, being heavy, it could not so 



