The Cyclostomes, or Lampreys 501 



against her side, and loops his tail over her near the vent and 

 down against the opposite side of her body so tightly that the 

 sand, accidentally coming between them, often wears the skin 

 entirely off of either or both at the place of closest contact. In 

 most observed instances the male pressed against the right 

 side of the female, although there is no unvarying rule as to 

 position. The pressure of the male thus aids to force the eggs 

 from the body of the female, which flow very easily when ripe. 

 The vents of the two lampreys are thus brought into close 

 proximity, and the conspicuous genital papilla of the male 

 serves to guide the milt directly to the issuing spawn. There 

 appears to be no true intromission, although definite observa- 

 tion of this feature is quite difficult, and, in fact, impossible. 

 During the time of actual pairing, which lasts but a few seconds, 

 both members of the pair exhibit tremendous excitement, 

 shaking their bodies in rapid vibrations and stirring up such a 

 cloud of sand with their tails that their eggs are at once con- 

 cealed and covered. As the eggs are adhesive and non-buoyant, 

 the sand that is stirred up adheres to them immediately and 

 covers most of them before the school of minnows in waiting 

 just below the nest can dart through the water and regale 

 themselves upon the eggs of these enemies of their race; but 

 woe to the eggs that are not at once concealed. We would 

 suggest that the function of the characteristic anal fin, which 

 is possessed only by the female, and only at this time of year, 

 may be to aid in this A^astly important process of stirring up 

 the sand as the eggs are expelled; and the explanation of the 

 absence of such a fin from the ventral side of the tail of the 

 male may be found in the fact that it could not be used for 

 the same purpose at the instant when most needed, since the 

 male is just then using his tail as a clasping organ to give him 

 an essential position in pairing. As soon as they shake together 

 they commence to move stones from one part of the nest to 

 another, to bring more loose sand down over their eggs. They 

 work at this from one to five minutes, then shake again, thus 

 making the intervals between mating from one to five minutes, 

 with a general average of about three and a half minutes. 



"Although their work of moving stones does not appear to 

 be systematic in reference to the placing of the pebbles, or 



