I IO JEAN DAWSON. 



of the mouth cavity. In this way the lamprey is enabled to 

 use the tongue in feeding without loosening its hold on its 

 host. 



33. After relaxation of the semiannularis muscle the food in 

 the oral hood of the attached lamprey is believed to be pumped 

 into the pharynx by the piston-like action of the tongue working 

 in the mouth cavity and to be forced thence into the oesophagus 

 by the contraction of the muscles of the pharyngeal wall. 



34. The intestine of a single specimen of Petromyzon niarimis 

 unicolor taken in December from Cayuga Lake, N. Y., was found 

 to contain not only blood but muscle, bone, the gill arch of a 

 small teieost and other tissues, probably those of the host to 

 which the animal had been attached. Gage's ('93) statement 

 that this species feeds only on blood of the host is thus erroneous. 



35. In P. inarinus, Lanipetra wilderi, and Ichyomyzon concolor 

 there projects forward into the pharynx from the cephalic end of 

 the united walls of the oesophagus and water tube a pair of jaw- 

 like structures, the velar jaws. 



36. The velar jaws are adjacent to the velar valves which 

 guard the opening from the pharynx into the water tube and the 

 two are supported by a continuous pincer-shaped cartilaginous 

 frame work, actuated by muscles in such a way that closure of the 

 velar valves approximates the velar jaws ; while opening of the 

 velar valves separates the velar jaws. 



37. When the attached lamprey is feeding, the velar valves 

 close the entrance of the water tube and thus prevent food from 

 entering the water tube and gill sacs. The velar jaws are closed 

 and it is believed passive during this process. 



38. The statement made by Giinther (1853) and Abbott (1875) 

 to the effect that the/m 1 lamprey feeds on fish and eggs or small 

 invertebrates are not supported by the examination of stomach 

 contents. 



39. It may be possible for the lamprey to feed when free on 

 minute forms or on somewhat larger animals siezed and held 

 between the approximated halves of the oral funnel. The minute 

 forms or the fragments resulting from the laceration of the larger 

 forms might then be carried to the pharynx by a current of water 

 entering the mouth. 



