92 JEAN DAWSON. 



the first attachment. When the lamprey becomes accustomed 

 to being handled it will seize one's finger and a strong suction 

 may be felt resulting from the action of the tongue in the process 

 of attachment. 



If the oral funnel of a recently dead lamprey be pressed against 

 the dish or finger, it becomes attached. If now one pulls the 

 body backward in a direction at right angles to the surface of the 

 attachment, it is found to be firmly attached. This attachment 

 is so firm that one may lift from the water a dead lamprey thus 

 adhering to the finger. If, instead of pulling the lamprey back- 

 ward or away from the surface, one pushes it in any direction 

 parallel to the plane of attachment, the oral funnel glides easily 

 over the surface of attachment. When the lamprey is attached 

 to a moving fish, the weight of the body as it drags through the 

 water exerts a backward pull on the lamprey in spite of which 

 the animal is able to maintain its hold, though at the same time 

 it is free to glide in any direction over its host. 



Since the dead lamprey remains attached, it is clear that the 

 maintenance of the vacuum which effects the attachment is not 

 through muscular action, but through mechanical means. Thus 

 it is probable that the living lamprey may at times remain 

 attached to the host without the expenditure of any muscular 

 energy. 



Is the vacuum by which the animal maintains its hold formed in 

 the mouth cavity alone or in both mouth and pharynx ? To deter- 

 mine this, the following experiments were tried on Lampctra u>il- 

 deri. (i) A capillary glass tube was fitted over a cambric needle 

 so as to form a small trocar. This was inserted into the nostril 

 of a lamprey and so directed that the needle pierced the dorsal 

 wall of the pharyngeal cavity. The needle was then withdrawn 

 leaving the tube in the opening. The tube was occasionally 

 cleaned by re-inserting the needle. The animal in which a com- 

 munication was thus established between the pharyngeal cavity 

 and the exterior was able to attach itself as firmly as before, thus 

 showing that the vacuum is formed not in the pharynx but farther 

 forward, /. i\, in the mouth cavity. 



(2) A glass tube was inserted into the mouth cavity of a second 

 lamprey between the lobes of the tongue. This tube was just long 



