368 OLIGOCHAETA 



(.'MAP. 



integumental blood capillaries. These are indeed for the most 

 part absent in the aquatic forms, being only faintly developed in 

 a few, an example possibly of degeneration. 



Earthworms and the Soil. Darwin has explained the 

 enormous effects which these soft -bodied and small creatures 

 have had upon the superficial structure of the earth. Their 

 castings, brought up to the surface, are blown about by the wind 

 when dry, and are thus spread over the ground in a fine layer. 

 It has been calculated that in the space of an acre *2 of an inch 

 in thickness of earth is annually brought to the surface. It is 

 clear therefore that in a long period of years there would be a 

 very large effect produced. On the sides of a hill this matter 

 brought up from below would tend to roll down the slopes when 

 dry, and would increase the debris carried away to the sea by 

 streams and rivers, so that continents formerly deposited under the 

 sea may owe no small proportion of their size to the continued 

 work of earthworms in past ages. 



Darwin has also pointed out the benefits to the agriculturist 

 which accrue from the industry of these Annelids. The soil is 

 thoroughly mixed and submitted to the action of the atmosphere. 

 The secretions of the worms themselves cannot but have a good 

 effect upon its fertility, while the burrows open up the deeper- 

 lying layers to the rain. Mr. Alvan Millson, 1 in detailing the 

 labours of the remarkable Yoruba worm (Siphonogaster millsoni 

 Beddard), hints that they may serve as a check upon the fatal 

 malaria of the west coast of Africa. By their incessant burrow- 

 ings and ejecting of the undigested remains of their food many 

 poisonous germs may be brought up from below, where they 

 flourish in the absence of sunlight and oxygen, and submitted to 

 the purifying influence of sun and air. 



Phosphorescence. Phosphorescence has been observed in 

 several species of Oligochaeta. The most noteworthy instance 

 of recent times is the discovery by Giard of the small worm 

 which he called Photodrilus phosphoreus at Wimereux. During 

 damp weather it was sufficient to disturb the gravel upon the 

 walks of a certain garden to excite the luminosity of these 

 Annelids. In all probability this species is identical with one 

 whose luminosity had been noticed some years before (in 1837) 

 by Duges, and named by him Lumbricus phosphoreus. According 

 1 Kcw Bull. Misc. Information, No. 46, 1890. 



