CH. l] EARTHWORMS AND LEECHES 13 



a conspicuous gush of coelomic fluid from the dorsal pores 

 in that region and an abundant secretion of mucus from 

 the skin itself. Thus the threatened region is, as it were, 

 isolated by ligatures from the rest of the body and all the 

 defensive resources at once brought to bear upon the 

 enemy. The coelomic fluid is alkaline and contains 

 crystals of calcium carbonate, and also contains micro- 

 organisms which when isolated and reared in artificial 

 cultures emit the characteristic smell of earthworms. It 

 is therefore not improbable that this odour is due to the 

 micro-organisms and not really a feature of the worm itself 

 (Lim Boon Keng) 1 . 



Special senses. Worms have no organs of special 

 sense in the usual acceptation of these words. They are 

 absolutely deaf to sound though very sensitive of vibrations 

 of the soil, or of the surface on which they are resting, 

 which fact at times causes it to appear that they do hear 

 certain notes, whereas in reality the note sounded has but 

 caused the surface in question to vibrate, and thus has 

 affected the worm. They possess no eyes, and yet they 

 can appreciate light and darkness and quickly move out 

 of a powerful light into shade. This sensitiveness to light 

 appears to reside only in the anterior regions of the body. 

 In some experiments which I conducted by flashing with 

 a small mirror a spot of light, obtained by an electric lamp, 

 on to a worm lying in the shade, a slight sensitiveness 

 seemed to coincide pretty closely with the darker pigmen- 

 tation that is so frequently observable on the first 15 or 20 

 segments of large worms, but the prostomium and first 



1 Phil. Trans. CLXXXVI. B. pt. 1. 



