IOS JEAN DAWSOK. 



but the writer has obtained no evidence that this is the ca.'-e, nor 

 does she see any reason to believe that during expiration there 

 is a movement of the water within the gill sac in the definite 

 manner indicated by Gage. 



19. In the attached Lampetra ivilderi and Ichthyomyzon con- 

 color in normal respiration, the ectal valve of Gage is relaxed, 

 that is, its free edge is not stretched and no other function is 

 observable in it than that of aiding in directing the expired current 

 of water. 



20. At the moment when Lampetra ivilderi or Ichthyomyzon 

 concolor detaches itself the dorso-ventral axis of the external 

 branchiopores is seen to elongate so that the free border of the ectal 

 valve is stretched taut. The ental valve at the same time strikes 

 against the inner surface of the ectal valve and is thus prevented 

 from turning outward. The external branchiopore is thus closed. 



21. The elongation of the dorso-ventral axis of the external 

 branchiopore is due to the contraction of the muscles, the ectal 

 and ental, which act upon the cartilaginous ring to which the 

 valves are attached. 



22. If the head of a Lampetra unldcri is above the surface of 

 the water, at the moment of detachment, a few drops of water 

 are seen to issue from the oral funnel. If the head of an attached 

 lamprey is far enough above the surface of the water so that 

 two or more branchiopores are exposed, air and water issue from 

 the mouth when the animal detaches itself. If carmine laden 

 water has been introduced into the gill sac of an attached animal 

 the head of which is submerged, a red stream is seen to issue 

 from the mouth at the moment of detachment. 



23. It is concluded from 20, 21 and 22, that detachment is 

 effected by a current of water directed forward from the gill sacs 

 through the water tube and pharynx so as to destroy the vacuum 

 in the mouth and oral funnel. 



24. If a thin mixture of carmine in water be introduced into the 

 gill sac of a free Lampetra ivilderi or /. concolor by means of a 

 pipette held opposite the external branchiopores, the fluid is ex- 

 pelled from the external branchiopores by contraction of the gill 

 sacs somewhat more violent than those of ordinary respiration. 



25. If a thick carmine mixture be introduced as under 24 it 



