97 
herrings and pilchards amongst fish ". Of the migra- 
tions of amphibia little is recorded. Turtles pro- 
bably wander occasionally in search of more abun- 
dant food. But by far the greater number of am- 
phibia hybernate. Frogs, however, migrate in vast 
numbers from their native waters about the end 
of July. They travel during the night, and conceal 
themselves by day, till they have dispersed them- 
selves widely through woods and meadows. Bing- 
ley, vol. ti. 392. &c. Of insects many perish, many 
hybernate, many migrate on the approach of the 
northern swinter*. The marine mollusca probably 
migrate in part from the shallower to the deeper 
waters in cold winters; many however hybernate. 
Plants migrate extensively ; not indeed as animals, 
by means of instinct operating upon will, but by the 
impulse and direction of that mighty Power to which 
the planets, the locusts, the swallows, and the storks, 
are equally obedient. Some migrate in the bowels 
of birds, as the misletoe; some on the wings of 
the wind, as the dandelion and the thistle, &c.: 
some on the waters, as the callitriche, the lemna, 
or duck-weed Y: the fucus natans, which floats over 
" For a curious account of the migrations of eels, see Sir H. 
Davy's Salmonia. 
x The vast swarms of locusts in Asia, Africa, and South 
America, need only be noticed in this place. The Ashmolean 
Lecture above mentioned refers to them with due detail. 
y The vallisneria spiralis is dioecious. The female plant pro- 
duces blossoms on long spiral stems, which enable them to rise 
to the surface of deep water. But the blossoms of the male 
plant, when ready to expand, detach themselves from the root and 
H 
