ZOOLOGY. 42'. J 



the wlieroaboiit.s of tbeir victim by couglomeratious of little pellets of 

 eartli here and there; aud kuowiugoues are wont to cautiously explore 

 localities so indicated Avith lanterns at night or in the early morning-, 

 and there lind the worms partly or entirely outside their holes. Few of 

 the many who liave learned thus much of the animal in question have 

 ever thought of the important functions in the economy of nature per- 

 formed by the humble being. Even as far back as 1837, hoAvever, Mr. 

 Darwin had appreciated the role that it plays and comuumicated to the 

 Geological Society of London a special memoir "On the Formation of 

 JNIould" by worms. Considerable skepticism was evoked respecting his 

 conclusions, so insignificant did the means appear to the end, but the 

 author published as his last contribution to science a special work on 

 the subject, and has fortified and amplified his early studies and con- 

 clusions. As Darwin says, some observant " farmers are aware that 

 objects of all kinds left on tlie surface of pasture land after a time 

 disappear, or, as they say, work themselves downward." This disap- 

 l)earance is of course due to no automatic process of the objects sinking- 

 down, but really to the cumulative effect of worms' castings. The 

 doubt such a statement may excite will be dissipated by a knowledge 

 of what a worm can do in a given period, and the multiplication of that 

 amount by number and time. 



Hensen, in experiments made on worms in confinement and fed on 

 leaves, found that they ejected about eight grains of earth a day; but, 

 according to Darwin, "a very much larger amount must be ejected b\ 

 worms in their natural state, at the x)eriods when they consume earth 

 as food Instead of leaves, and when they are making deep burrows.'^ 

 In corroboration of this opinion, Darwin has tabulated the results of 

 numerous observations on the "weight of the castings accumulated at 

 the mouth of a single burrow." Before weighing, the castings were 

 dried (excepting in one specified instance) by exposure during many 

 days to the sun or before a hot fire." These castings for each hole 

 "generally exceeded an ounce in weight after being dried, and some- 

 times nearly equaled a quarter of a pound. On the Nilgiri Mountains- 

 one casting even exceeded this latter weight. The largest castings in 

 England were found on extremely poor pasture land; and these are 

 generally larger than those on land producing a rich vegetation. It 

 would appear that worms have to swallow a greater amount of earth 

 on poor than on rich land, in order to obtain sufficient nutriment." (P. 

 1G2.) In another place we are tokl that Hensen found that "there 

 nuist exist 133,000 living worms in a hectare of land, or 53,767 in an 

 acre. This latter number of worms would weigh 350 pounds, taking 

 Hensen's standard of the weight of a single worm, namely, one gram. 

 It should, however, be noted, says Mr. Darwin, " that this calculation 

 is founded ®n the numbers found in a garden, and Ilensen believes that 

 worms are twice as numerous in gardens as in cornfields." On the 



