48 
crocodile attains the length of twenty-five feet, the 
alligator of eighteen; the lacerta agilis does not 
exceed six inches; the green tree frog is about two 
inches and a half. Among fish, sharks of thirty 
feet in length have been seen. The stickle back, 
like the tree frog, trochilus, and mus messorius, is 
rarely found to exceed two inches and a half. Lob- 
sters have been found two feet in length, monoculus 
polyphemus of four feet, shrimps rarely of two 
inches. Amongst insects, a species of mantis is 
found nearly a foot in length; centipedes are seen 
of eight or ten inches. The acarus, or mite, is a 
giant amongst his kind, if he reaches the dimension 
of one twentieth part of an inch. Among mollusca, 
the sepia octopodia is said to possess arms of thirty 
feet in length; and the Gordius marinus is said to 
stretch its slender form to an equal extent. The 
slug, inhabiting the least nerita, scarce exceeds an 
eighth of an inch ; the infusoria perhaps barely equal 
a thousandth. Thus among plants, the larch ex- 
ceeds 100 feet in height, the araucaria 200, the lam- 
bert pine 215 feet: the lichen jolithus appears to 
be a mere purple pigment on the stone to which it 
adheres. 
Colours. 
The primary object of sight, even before distinct 
form is seen, is colour. Visible form indeed (as 
painters know full well) is only an enlightened, 
bounded by a shadowed, portion of space, or one 
colour limited by another. Faintness of light, di- 
