IO6 JEAN DAWSON. 



stoppage of the inflowing stream of water. If the velar valves were 

 then opened, the jaws would open and the food would be released 

 and if at the same time the oesophagus should open by relaxation 

 of the posterior pharyngeus muscle, the jaws lie so near the open- 

 ing of the oesophagus that the food with a small quantity of 

 water would be swept into the oesophagus. The more one con- 

 siders the mechanism, the more does the conviction deepen that 

 the lamprey is able to feed by means of a water current through 

 the mouth and by the aid of the velar jaw. 



SUMMARY. 



1. When Lampctra wilderi is swimming, the sides of the oral 

 funnel are approximated so that the opening into it is reduced to 

 a narrow vertical slit, fringed by the oral cirri. The compressed 

 oral funnel then serves as a vertical wedge-shaped cut-water. 



2. When Lampetra wilderi is about to attach itself to any 

 surface, the oral funnel is spread and applied to the surface with 

 a quick backward and forward movement of the tongue and the 

 animal becomes attached. 



3. If an opening is made between the pharyngeal cavity and 

 the exterior in Lampctra wilderi, the animal is still able to attach 

 itself in the same manner as though uninjured. 



4. If a communication be established between the mouth cavity 

 or cavity of the oral funnel and the pharyngeal cavity or the ex- 

 terior, the animal is unable to attach itself. 



5. Attachment in Lampetra wilderi is therefore effected by 

 means of a partial vacuum created in the cavities of the oral 

 funnel and mouth by piston-like action of the tongue. 



6. A dead Lampetra ivilderi becomes firmly attached when its 

 oral funnel is pressed against a surface with the fingers, and re- 

 mains thus attached. 



7. It follows from six that an attached Lampetra wilderi does 

 not necessarily exert muscular energy to maintain its hold. 



8. The oral funnel of a dead or living Lampetra ivilderi may 

 be moved about freely and very easily over the surface to which 

 it is attached so that the animal is enabled to glide over the sur- 

 face of its host and so change its position with ease. 



9. The oral funnel of a dead or living Lampctra wilderi may 



