94 JEAN DAWSON. 



In the case of the dead lamprey, the pumping action of the 

 tongue must be replaced by the pressure exerted by the fingers 

 against the oral funnel in the act of attaching the animal, the 

 tongue then remains in the back part of the mouth cavity and 

 thus functions in place of the semiannularis to close the com- 

 munication between the mouth cavity and the pharynx. 



B. Mode of Feeding of Attached Lampreys. This has never 

 been observed, nor is it likely to be, so that our knowledge of 

 the process of feeding is an inference from the structures in- 

 volved. The moment the animal attaches itself the oral funnel 

 is opened quickly and is pressed flat against the supporting sur- 

 face. The process may be watched when the lamprey attaches 

 itself to the sides of a glass dish. The funnel may be so much 

 flattened that the teeth on the tongue press against the glass. 



In this position the teeth of the oral funnel and tongue consti- 

 tute a very efficient rasping apparatus. Fiirbringer (1875) has 

 shown how the teeth of the funnel are moved in and out on radial 

 lines by the action of the inner layer of the annularis muscle. 

 The arrangement of teeth as already pointed out is such that in 

 their movement along radial lines they necessarily lacerate every 

 part of the surface covered by the funnel. It will be shown be- 

 low that the tissues of the host are thus reduced to a fine pulp, 

 which is then swallowed. 



We may infer that this pulp finds its way into the pharyngeal 

 cavity by the pumping action of the tongue. The considerable 

 size of the pharnygeal cavity (Fig. 4) and the distensibility of its 

 walls enable it to accommodate a large amount of food. By the 

 contraction of the muscular wall, particularly the pharyngeus 

 muscle and the basilaris muscles, the food is forced back into the 

 oesophagus, while the posterior pharyngeus muscle relaxes to 

 permit its passage. 



C. Character of Food. As regards the character of the food, 

 there is much difference of opinion. Giinther (1853) says : " Die 

 Nahrung des Neunauges besteht ausser Wurmerri, Insekten, etc. 

 noch in Fischen, sowohl kleinen, als grossern, an welche sie sich 

 wie an Steine festsaugen." Giinther does not indicate that he 

 makes this statement from the examination of stomach contents 

 of the lamprey, so that it is possibly merely a current belief. 



