322 TRANSACTIONS OF THE [mAY 10, 



pocket, less than a foot in diameter, lyins^ between a number of 

 large rounded stones. The water, 66° F. in temperature, was 

 sweeping across it in a moderatel}' strong current. The tem- 

 perature of the air at the time was 70° F. The water-depth in 

 the nest was about ten inches. 



The lampreys were in constant movement, sometimes crowd- 

 ing closely together, ten or twelve in number, now and again 

 scattering, manj^ leaving the nest and others returning. Oc- 

 casionally the nest would be almost deserted. The greatest 

 number was observed about noon-time. The entire party seemed 

 to devote its attention to transporting gravel : the spawning 

 process occurred at irregular intervals and was of very short 

 duration. At first it proved difficult to distinguish males and 

 females. Thej^ are almost equal in size and thickness, and the 

 slight differences in fin-characters could not well be seen when the 

 animal was in motion. So too, the erected urinogenital papilla of 

 the male was onh' occasionally distinguishable. It was later evi- 

 dent, however, that the males were by far the more numerous. 

 Examination of the lampre3's taken from this neighborhood, but 

 not from the nest alone, showed that the proportion of males to 

 females was about .5 to 1. It is a reasonable inference, therefore, 

 that this species is polyandrous although this could not be veri- 

 fied in the present instance, the active movements of the animals 

 preventing the observer from following the male till its return to 

 the same female. The mode of mating could, however, be 

 clearly followed. The female, after many circlings about the 

 nest, attaches to a stone and is apparently struggling to move it. 

 Then a male, which up to this point has been diligently stone- 

 moving and is now close by, suddenl}'^ seizes his mate " some- 

 where near the head, he then winds himself half way round the 

 female whereupon the two bend theii- tails downward and stir up 

 the sand bj^ the most vigorous movements " (Gage). 



The actual position of a i)air during copulation is shown in 

 the plate. The male attaches the oral disc to the back of the 

 head of a female, somewhat in front of the eye and slightly on 

 the right side. The back of the male is then instantly arched 

 and the tail region wound around the hinder trunk of the female, 

 forming one turn of a left handed spiral. Its increasing curve 

 toward the tail causes the bod}- of the male to here lie at right 

 angles to that of the female. This position was verified in 

 eleven instances. In only one case the body of the male 

 appeared to be wound in the reverse direction. During this 

 process, the body of the male is so rotated that the urino, 

 genital papilla becomes apposed to the cloaca of the female- 

 this result being aided b}' an upward arching of the latter's body. 



