SYSTEM OF NATURE. 
87 
animal-plants applies only to a fractional part of the al¬ 
most numberless tribes of beings which are included in 
this primary division of animals. Like fishes, they are 
perfectly destitute of organs adapted for progressive mo¬ 
tion on land. Each group is remarkable for its want of 
limbs. 
5thly. Ambulantia. The general appearance of any 
shell-bearing mollusk crawling slowly on its belly, its head 
and tail alone protruding from its heavy, solid and com¬ 
pact shell, certainly brings forcibly to our recollection the 
figure, proverbial slowness, and mountainous covering of 
a tortoise, The terrestrial Mollusca devour food similar 
to that devoured by the tortoises ; their greediness in 
feeding is similar; their capability of fasting similar ; 
their tenacity of life similar. The resemblance is not 
entirely that of general economy; on the contrary, in 
the Cephalopods, there is a structural similarity : the 
mouth is something like that of a tortoise ; it is composed 
of two strong, horny, toothless jaws, the lower closely 
fitted in a groove of the upper: the tongue, ear and eye, 
also present considerable resemblance. The mode of re¬ 
production, by means of comparatively large and nearly 
spherical eggs confided to the earth, is also similar. 
Gthly. Repentia. The general figure of worms — 
whether we regard the true earth-worms or the somewhat 
aberrant leeches and other tribes, their elongate form, 
their want of legs, their wriggling progressive motion — 
seems to be represented with perfect fidelity by the entire 
class of scaly reptiles ; and if we compare more accu¬ 
rately the structure of Caecilia and Lumbricus, and remark 
the irregularity with which the bodies of both are divided 
into rings, we cannot but be struck with a similarity which 
