2 EARTHWORMS AND LEECHES [CH. I 



The sides of the burrow are kept moist by slime dis- 

 charged from the glandular cells of the skin, and perhaps 

 by liquid discharged from the body-cavity through the 

 dorsal pores which occur in the grooves that separate 

 segment from segment. The slime is said to possess 

 antiseptic properties, and thus to preserve the skin of the 

 worm from harmful bacteria. 



The mouth of the burrow is guarded by small stones 

 or more frequently by one or more leaves pulled in to a 

 greater or less distance. Fir-needles, stalks of horse- 

 chestnut leaves and other similar things are often to be 

 seen standing nearly erect upon the ground, their lower ends 

 having been forcibly dragged into the mouth of a burrow 

 by a worm. On still, warm nights in early autumn the 

 rustling noise of fallen leaves being dragged along by 

 worms is often plainly audible in favourable localities. 

 Darwin has pointed out 1 that worms exhibit considerable 

 intelligence in drawing the narrow end of leaves of various 

 shapes foremost into the burrow : leaves with broad bases 

 and narrow apices are generally pulled in tip first, whereas 

 when the base is narrower than the apex the reverse 

 position is usually found. There is no doubt that worms 

 can judge which end of any leaf is the better to seize. 

 The reason for thus pulling objects into the entrance of 

 the burrow is probably to prevent the entry of foes, 

 centipedes, parasitic flies, etc., to keep the burrow moist 

 by preventing evaporation, to keep out the cold lower 

 strata of air at night, to bring food supplies within safe 

 reach, and also to enable the worm to lie near the mouth 

 1 Vegetable Mould and Earthworms. London, 1881. 



