55 2 
LOWEST VERTEBRATES. 
municate with the pharynx by a common opening to which the ducts of all con¬ 
verge. The intestine is furnished with a spiral valve, and the eggs are minute. 
The true lampreys are characterised in the adult condition by having two 
dorsal fins, the hindmost of which is continuous with the caudal; and likewise by 
the upper series of oral teeth consisting either of a doubly-cusped transverse ridge, 
or of two closely-placed separate teeth; while the teeth on the tongue are serrated. 
The genus appears to be represented by four species, which are confined to the 
coasts and fresh waters of the Northern Hemisphere, ranging as far south as West 
Africa. The largest of these is the sea-lamprey, represented in the upper figure of 
our illustration, which may grow to as much as a yard in length, and is common to 
Europe, North America, and West Africa. On the other hand, the river-lamprey, 
or lampern, which at certain seasons ascends the rivers of Europe, North America, 
and Japan in innumerable hosts, is somewhat less than two feet in length, and differs 
from the last species in being uniformly coloured, instead of marbled with black. 
Still smaller is the small lamprey, also known as the pride or sand-piper, which is 
likewise common to Europe and Western North America, and scarcely reaches one 
foot in length; its coloration being uniform. The young of this form was long 
regarded as a distinct genus, under the name of Ammoccetes ; but its true nature 
was discovered by watching the transformation into the adult. The larva, writes 
Dr. Gunther, requires three or four years for its full development. At first the 
head is very small, and the cavity of the mouth “ surrounded by a semicircular 
upper lip, the separate lower lip being very small. There are no teeth, but several 
fringed barbels surround the mouth. The extremely small eyes are hidden in a 
shallow grove ; but there is a median single nasal opening, and seven gill-openings, 
as in the adult. The vertical fins form a continuous fringe, in which the later 
divisions are more or less distinctly indicated.” When open, the mouth of lampreys 
is nearly circular in shape, but when closed forms a narrow slit. 
Much has still to be learned regarding the habits of lampreys, but it appears 
that all the members of the present genus ascend rivers for the purpose of spawn¬ 
ing, and that some of them pass the whole of their larval conditions in fresh waters. 
They are all carnivorous, and in the adult state attach themselves by their mouths 
to the bodies of fishes, from which they rasp off the flesh with their horny teeth ; 
fish being not unfrequently met with bearing the scars of wounds thus inflicted, 
and a salmon has been taken high up in the Rhone with a sea-lamprey tightly 
adhering to its side. Bathers have also been known to be attacked by the same 
species. Commonly keeping to the bottom, the sea-lamprey may at times be seen 
swimming near the surface with a serpentine movement of the body. In the 
Severn the capture of this species lasts from February to May, while in the Thames 
the season is May and June ; but in the Scottish rivers the lampreys do not ascend 
till the end of June, remaining till the beginning of August. During the spawn¬ 
ing-season these fishes excavate furrows in the river-bottoms for the reception of 
their eggs, and are said to remove impeding stones by lifting them up with their 
sucking-mouths. Being much exhausted by the function of spawning, at its con¬ 
clusion they make their way with all speed to the sea. The river-lamprey was 
at one time thought to be a permanent inhabitant of fresh waters, but it has been 
taken in the sea, and it has even been considered that it may undergo its meta- 
