MUSSEL CLIMBING. 331 
within its own type, characteristics of lower forms of life; 
and thus do all the higher animals in their embryonic condi- 
tion, pass through stages representing the lower vertebrates. 
MUSSEL CLIMBING. 
BY REV. S. LOCKWOOD, PH.D. 
Can any one see a snail travel, and not del mentally, 
“how it does it?” The method certainly is curious. A 
fleshy disk is protruded, and caused to project in the direc- 
tion of locomotion; it is then spread out flatly, and while 
slightly adhering to the object over which it is passing, a 
contractile energy is exerted, and the little animal bearing 
its house is drawn onward. Thus by the repeated protru- 
sion, expansion, and contraction of this soft organ, in due 
time its journey is accomplished. Because of this method 
of progression on a ventral disk, all those shell-fish, or 
properly speaking, molluscan animals, so constituted, are 
called by the systematists, gasteropods, a term which means 
ventral-footed. And in rank these gasteropods stand next 
to the most highly organized of the mollusca. But some of 
these shell-encased creatures do not travel at all. Take, for 
instance, the oyster, called a monomyary, because the valves 
are held together by a single muscle. This sedate bivalve 
once settled, probably never moves from that spot. But a 
