142 
ZOOLOGY. 
The ovaries and male glands (the sexes being distinct) 
are unpaired plates suspended from the back-bone, and have 
no ducts, the eggs breaking through the walls of the ovary, 
falling into the abdominal cavity and passing out of the 
abdominal pore. The eggs of Myxine are very large in 
proportion to the fish, enclosed in a homy shell, with a fila- 
ment at each end by which it may adhere to objects. 
The hag-fish is about a foot long and an inch thick, with 
the head small, a median palatine tooth, and two comb-like 
rows of teeth on the tongue. There is a single gill-opening 
a long way behind the head; there are large mucous or 
slime-glands on the side of the body, for these fishes are 
very slimy. The hag lives at considerable depths in the 
sea; we have dredged one at 114 fathoms in soft deep mud 
ofE Cape Ann. It is often parasitic, attaching itself to the 
bodies of fish, and has been found to have made its way 
into the body-cavity of sturgeons and haddock. 
The lamprey lives both in fresh and salt water. The 
eggs of the common lamprey, Petrornyzon mari7iics (Linn.), 
are laid in early spring, the fish following the shad up the 
rivers, and spawning in fresh water, seeking the sea in 
autumn; small individuals, from five to seven inches long, 
have been seen by Dr. Abbott attached to the bellies of 
shad, sucking the eggs out of the oviducts. 
The lamprey when six inches long is quite unlike the 
adult, being blind, the eyes being concealed by the skin; 
it is toothless, and has other peculiarities. It is so strangely 
unlike the adult that it was described as a different genus 
(Ammomfes). P, Jiigricans Lesueur is smaller, and oc- 
curs in the lakes of New York and eastward, wh le P, niger 
Eafinesque is still smaller, and lives in the Western States. 
Class IV. — Pisces {Sliarhs, Rays, Sturgeons, Garpikes, 
and bo ny fishes). 
General Characters of Fishes. — We now come to verte- 
brates which have genuine jaw-bones and fins in pairs, and 
