288 



THE AMERICAN NATURALIST 



[Vol. XLI 



outlet of the tank, closing it, and in a few moments a half inch of 

 water had accumulated over the bottom of the tank. Thereupon 

 the skates set up an energetic spouting of water from the spiracles, 

 — a mode of behavior which had never before come to my notice. 

 At frequent intervals a large stream of water was ejected from each 

 spiracle, rising vertically to a height of one or two inches. (The 

 fish were of uniform size, — about a foot in width across the pectoral 

 fins.) The animals were not submerged, it should be remembered, 

 but were less than half covered with water, most of the dorsal 

 surface, including the spiracular region, being well out. The 

 vigor and frequency of the spouting and the fact that so many 

 skates were doing it at the same time produced an effect striking 

 enough to compel attention. No doubt this behavior has been 

 observed previously by others. A "Spritzloch" is certainly a 

 spout-hole. But I could recall having met only the briefest 

 reference to the use of the elasmobranch spiracle in respiration, 

 so I postponed the fate of some of the skates and placed them in an 

 aquarium suppHed with running sea water, with ;i v'ww to watching 

 their respiratory movements. During the nexi tVw days I observed 

 the fish as I could, but other work had ])rc( ('(lcii( (\ so ihat i was 

 unable to carry on any systematic study of tlicir behavior. How- 

 ever, my impromptu experiments broiioht to li<;lit one or two 

 facts which seem to me worthy of iiu niion. 



As must be well known, the modified first visceral cleft (si)iracle) 

 serves in the skate chiefly as an iiicurrciit opctiino- tor the rcsjjira- 

 tory stream. So far as this function i.> concerned, as poiiucd out 

 by Garman (74), the spiracle is probably of greater importance 

 in the rays than in the sharks, owing to the fact that the rays, for 

 the most part, lie flat upon the bottom of the sea, and this habit 

 places the mouth at a disadvantage as an incurrent respiratory 

 opening, while in the perpetually roving sharks such is not the case. 

 These facts are very likely connected with the fact that the spiracles 

 occur as large openings in all the rays while in many of the sharks 

 they are either very small or completely close.!. 



Many writers make the statement that water may pass either 



notes that, whereas the sting-rays have in the spiracular passage a 

 valvular fold preventing outflow, in the common skate no such 



