ANNELIDS. 
439 
Sparsely-Bristled Group, —Order Oligochzeta. 
The most familiar representatives of this group are the earth-worms 
( Lumbricidce ), characterised by the numerous short segments of the body, the 
bullet-shaped, plastic head-lobe, and the hook-like bristles which form either two 
or four longitudinal rows, and project but slightly above the surface of the skin. 
common earth-worm, Lumhricus agricola (nat. size). 
Apart from certain thickenings of the skin, earth-worms have no special organs 
of sense, that is to say, neither ears nor eyes, although at the same time they are 
highly sensitive to the influence of light. Their food consists for the most part of 
the decaying animal and vegetable matter absorbed from the soil, which they take 
in large quantities into the alimentary canal; but they also draw into their 
burrows straws, feathers, leaves, bits of paper, etc., to serve for food. The muscular 
strength required to overcome such obstacles is often very great, and no one would 
suppose that a creature so soft, slimy, and to all appearance helpless would be 
capable of the effort; but the muscular system of these animals is in reality highly 
developed, as is shown by the strenuous resistance offered to any attempt to drag 
them from their burrows. 
In Britain there appear to be about twenty kinds belonging to three genera, of 
which the richest in species are Allolobophora and Lumbricus, Allurus including 
only the square-tailed worm. Earth-worms appear to be spread over all the tropical 
and temperate parts of the world, and in some countries attain a size far surpassing 
that of the English species; one of the largest (Microchceta rappi ) being an 
inhabitant of South Africa. The average length of this creature is 4 or 5 feet, 
