BREATHING MECHANISM OF THE LAMPREYS. 95 



Abbott (1875, p. 827), speaking of Petrotnyzon marinns says : 

 " This fish which is found occasionally hibernating in the soft 

 mud at the mouths of some of the inflowing creeks appears to 

 come from the bay or ocean (at any rate from the lower portion 

 of the river) in immense numbers early in March and remains 

 about the rocks at the head of tide water for some time as 

 though waiting for the coming shad or herring. With the shad 

 they pass up the river beyond tide-water, and in the rapid rocky 

 portions of the river having deposited their own ova, they wander 

 over the breeding grounds of other fishes and devour every egg 

 they can find. I have found lampreys in Crosswicks Creek in 

 the month of May gathering up the eggs from sun fish nests." 

 But here again the observation is not supported by an exami- 

 nation of stomach contents. 



The only other observation known to me is that of Gage 

 (1893) on P. inarimts nnicolor. "Of all the specimens obtained 

 out of the breeding season either the digesting part of the ali- 

 mentary canal was empty or it contained blood. No partly 

 digested worms or insects or small fish or parts of fish flesh were 

 found, although diligent search was made ; consequently it is 

 believed that the lake lamprey is wholly parasitic during its adult 

 life and lives on blood sucked from other fishes." Again (p. 

 438) he speaks as follows of the intestine at the breeding season : 

 " The atrophy takes place within two weeks, and begins at the 

 terminal extremity, and extends gradually cephalad until the 

 whole canal appears like a thread. As no food is taken during 

 the spawning season there is no necessity for digestion, and in 

 the female there is no room for the intestine when the ova are 

 completely matured." 



As it seemed incredible that the very elaborate rasping appa- 

 ratus of this lamprey could have no other use than to enable the 

 animal to produce a raw surface from which to suck blood, a 

 thorough investigation of all the material of P. marinus at hand 

 was made. But in all cases the intestines were found to be empty 

 and atrophied. It was then learned that all the available lam- 

 preys had been caught in the breeding season. Through the 

 kindness of Professors Gage and Wilder, however, I obtained 

 several specimens of Pctroinyzon marinus unicolor taken in the 



