" Were one to visit Yoruba during the early part of the rainy sea- 

 son only, it would appear impossible to account for these facts 



while under our feet unnoticed was going on the ceaseless labor of the 

 real fertilizers of the land. 



" In the dry season the mystery is at once solved, and in the sim- 

 plest and most unexpected manner. The whole surface of the ground 

 among the grass is seen to be covered by serried ranks of cylindrical 

 worm casts. These worm casts vary in height from a quarter of an 

 inch to three inches, and exist in astonishing numbers. It is in many 

 places impossible to press your finger upon the ground without touch- 

 ing one. For scores of square miles they crowd the land, closely 

 packx-d. upright, and burned by the sun into rigid rolls of hardened 

 clay. There they stand until the rains break them down into a fine 

 powder, rich in plant food, and lending itself easily to the hoe of the 

 farmer. Having carefully removed the worm casts of one season from 

 two separate square feet of land at a considerable distance from one 

 another, and chosen at random, I find the result to weigh not less than 

 ten and three-quarters pounds in a thoroughly dry state. This gives 

 a mean of over five pounds per square foot. Accepting this as the 

 amount of earth brought to the surface every year by these worms, we 

 get somewhat startling results. I may say, speaking from the result 

 of numerous experiments, that five pounds is a very moderate yearly 

 estimate of the work done by these busy laborers on each square foot 

 of soil. Even at this moderate estimate, however, of the annual result 

 of their work, we have a total of not less than 62,233 tons of subsoil 

 brought to the surface on each square mile of cultivatable land in the 

 Yoruba country year after year, and to the untiring labors of its 

 earth-worms this part of West Africa owes the livelihood of its people. 

 Where the worms do not work, the Yoruba knows that it is useless to 

 make his farm. 



" Estimating one square yard of dry earth by two feet deep as 

 weighing half a ton, we have an annual movement of earth per square 

 yard to the depth of two feet, amounting to not less than forty-five 

 pounds. From this it appears that every particle of earth in each ton 

 of soil to the depth of two feet is brought to the surface once in twenty- 

 seven years. 



" The earth-worm which produces such surprising results has been 

 identified as a new species of Siphonogaster, a genus known hitherto 

 only in the i^ile Valley." 



