45 o CYCLOSTOMATA 



represented both in the rivers and the seas of Europe, Asia, 

 North and South America, and Australia. 



There is no doubt as to the exclusively marine character of 

 Myxinoids, but the case of the lampreys is more difficult. As 

 all of them, so far as we know, ascend rivers for spawning, and 

 as the environment of the young is usually indicative of the 

 original home of the parents, it is likely that the lampreys repre- 

 sent a fresh-water Cyclostome stock. It may be recalled that the 

 salmon, first cousin to the trout, and essentially a fresh-water 

 fish, spawns in the rivers, though it does most of its feeding and 

 growing in the sea. On the other hand, the common eel is 

 essentially a deep-water marine fish and spawns in the great 

 abysses, though it does most of its feeding and growing in the 

 fresh waters. Although various authorities state with some 

 emphasis that most lampreys are marine, it is more probable 

 that the Petromyzonts represent a section of the old Cyclostome 

 race that took upon itself the problem of trying the fresh waters 

 for what they were worth. This may serve to illustrate the 

 zigzagness of pedigrees. The main stock of Chordates was 

 undoubtedly marine ; the lampreys, primarily adapted to the 

 " Sturm und Drang " of littoral life, went upstream ; a large 

 number became fresh-water animals. They visit the sea, like the 

 salmon, to feed and grow lusty ; they visit the fresh water to 

 spawn and die ! 



Lampreys are carnivorous, and most of them are in the 

 habit of fixing themselves to the bodies of fishes by means 

 of their suctorial mouth-funnel, rasping off scales and skin 

 and muscle with their teeth, and then sucking in the blood 

 and pieces of loosened flesh. They take a very firm hold 

 of their victims, and are difficult to dislodge. Experiments 

 by Miss Dawson {Biological Bulletin, ix., 1905, pp. 1-21, 

 91-111) show that the funnel of a dead brook-lamprey (Lam- 

 petra wilderi) becomes firmly attached to a perfectly smooth 

 surface when pressed against it with the fingers ; how much 

 more firmly will the muscular funnel of the living animal 

 adhere. It seems, too, from Miss Dawson's experiments that 

 a lamprey can shift its hold of the fish without actually loosen- 

 ing it. They most frequently attach themselves on the side 

 under the pectoral fin, and "their hold is probably seldom 

 loosened by any fish except by accident ". " The relentless 



