BREATHING MECHANISM OF THE LAMPREYS. IOI 



mouth and out through the external branchiopores. After a 

 few inhalations, the current would be reversed and a stream of 

 water would be sent out of the mouth with some violence as 

 though the carmine in the water was found to be irritating. The 

 current of water passing into the mouth, it will be remembered, 

 was not seen in the L. wildcri. 



The two specimens were kept alive for five weeks in the labor- 

 atory when they died after being attacked by fungus. During 

 their life in the aquarium, they were not observed to have taken 

 any food, although large pieces of raw beef were suspended in 

 the aquarium. 



The only advantage to the lamprey of an inspired current 

 through the mouth would lie in the fact that by means of such a 

 current food might be caused to enter the mouth when the animal 

 was free. The experiment on the inspiration of water through the 

 mouth in L. wilderi above recorded was necessarily performed 

 during the breeding season when the brook lamprey takes no 

 food. It is therefore inconclusive. The similar experiment on /. 

 concolor performed out of breeding season would tend to support 

 the statement of Giinther (1853) and Abbott (1875) that the 

 lampreys feed when free as such feeding could hardly be accom- 

 plished without the inspired current through the mouth. 



C. Dctaclnnent and Rcgnrgitation. The valves of the external 

 branchiopores are clearly useless in aiding the animal to draw 

 water into the mouth. There remains but one use for these 

 structures, namely, to render possible an expired current through 

 the mouth. 



When the lamprey is firmly attached there is a partial vacuum 

 in the mouth cavity and the oral hood. It would require con- 

 siderable force for the animal to tear itself free when thus at- 

 tached, but if by closing the external branchiopore and opening 

 the velar valves and mouth it can force water into the oral fun- 

 nel from the gill sacs, the vacuum will be at once destroyed and 

 the animal may free itself without great muscular exertion. 

 There is a further possible advantage to the animal in being able 

 to expel a current of water from the gill sacs through the mouth. 

 Such a current would enable it to cleanse the pharynx and 

 mouth of indigestible and bulky food particles, nor does there 

 appear to be any other means of accomplishing this. 



