40 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
“ black glands,” as also in tlie characters of the antennary-cirri and 
parapodia. 
The Work of Earthworms on the African Coast.— The ‘ Kew 
Bulletin’ * of October last contains a report by Mr. Alvan Millson, the 
Assistant Colonial Secretary of Lagos, on Yorubaland, the native 
territory adjacent to Lagos. After describing the wasteful system of 
cultivation employed by the natives and the wonderful rapidity with 
which the soil recovers from it, he says the mystery is solved in a 
simple and unexpected manner during the dry season. The whole 
surface of the ground beneath the grass is seen to be covered by rows of 
cylindrical worm-casts. These vary in height from 1/4 in. to 3 in., 
and exist in astonishing numbers. It is in many places impossible to 
press a finger upon the ground without touching one. For scores of 
square miles they cover the surface of the soil, closely packed, upright, 
and burned by the sun into rigid rolls of hardened clay. The rains 
ultimately break them down into a fine powder, rich in plant-food and 
lending itself easily to the hoe of the farmer. On digging down the 
soil is found to be drilled in all directions by a countless multitude of 
worm-drills, while from 13 in. to 2 ft. in depth the worms are found in 
great numbers in the moist subsoil. 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, Mr. 
Millson found the weight to be lOf lb., in a thoroughly dry state. 
This gives a mean of over 5 lb. per square foot and a total of not less 
than 62,233 tons of subsoil brought to the surface on each square mile 
of cultivable land in the Yoruba country every year. This work goes 
on unceasingly year after year, and to the untiring labours 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 2 ft. deep 
as weighing half a ton, there is an annual movement of earth per square 
yard of the depth of 2 ft., amounting to not less than 45 lb. From this 
it appears that every particle of earth in each ton of soil to the depth 
of 2 ft. is brought to the surface once in twenty-seven years. It seems 
more than probable that the comparative freedom of this part of West 
Africa from dangerous malarial fevers is doe, in part at least, to the 
work of earthworms in ventilating and constantly bringing to the surface 
the soil in which the malarial germs live and breed. From specimens 
which Mr. Millson has sent home it appears the worm belongs to a new 
species of the genus Siphonogaster. 
Trigaster and Benhamia.t — Dr. W. B. Benham has altered his 
conclusion that Benhamia of Michaelsen is synonymous with Trigaster 
Benham. They are, perhaps, both subgenera of Acanthodrilus , with 
which (and with Deinodrilus') they have in common the following 
characters — The nephridia are in the form of a network ; there are 
two pairs of coiled cylindrical prostates in somites xvii. and xix., and 
there are two pairs of spermathecae. In Trigaster the clitellum is 
exceedingly long and extends over somites xiii.-xl. ; in Benhamia it 
* ‘ Bulletin of Miscellaneous Information,’ 1890, pp. 243-4. 
t Ann. and Mag. Nat. Hist., vi. (1890) pp. 414-7. 
