2 9 2 THE POPULAR SCIENCE MONTHLY. 



its hole, it drags leaf -stalks in by the base so as to fill it faster ; but as 

 soon as it comes to close quarters, it turns and drags the rest of the 

 stalks in by the tips. Triangles of paper were given worms instead 

 of leaves, and they likewise drew them in in the easiest way, appar- 

 ently at the first trial. When worms can not obtain leaves, petioles, 

 sticks, etc., with which to plug up the mouths of their burrows, they 

 often protect them by little heaps of stones ; and such heaps of smooth, 

 rounded pebbles may frequently be seen in gravel-walks. A lady in- 

 terested in this study removed the little heaps of stones from the 

 mouths of several burrows, and cleared the surface of the ground for 

 some inches all around. She went out on the following night with a 

 lantern, and saw the worms, with their tails fixed in their burrows, 

 dragging the stones inward by the aid of their mouths. After two 

 nights some of the holes had eight or nine small stones over them ; 

 after four nights one burrow had about thirty and another thirty-four 

 stones, and one of the stones weighed two ounces. The strength of 

 worms is also shown by their often displacing stones in a well-trodden 

 gravel-walk, a task that sometimes demands considerable effort. 



Worms excavate their burrows in two ways : by pushing away the 

 earth on all sides wkei'e the ground is loose or onlj- moderately com- 

 pact, and where they are able to disappear from sight with surprising 

 agility ; and by swallowing the dirt, where the ground is hard, and 

 ejecting the swallowed earth afterward in the form of the " castings " 

 which are found at the mouths of their burrows. Worms also swal- 

 low earth to extract the nutritous matter which may be contained in 

 it, and in larger quantity than for making their burrows ; and the res- 

 idue of this, after the nutriment is extracted, is also cast out. The 

 deposition of castings, then, is no insignificant part of the labor that 

 they perform, and leaves very perceptible traces upon the surface. 

 The castings may be seen by any one who will take the pains to look 

 for them, and often in garden-walks without looking for them, piled 

 up in the shape of towers of greater or less height around the bur- 

 rows. The towers formed by a naturalized East Indian worm, at 

 Nice, France, which are sometimes distributed as thickly as five or 

 six to a square foot, are built to a height of from two and a half to 

 three inches. The tower of a perichceta in the Botanic Garden at 

 Calcutta, of which Fig. 2 is an exact representation, measured three 

 and a half inches high and 1*35 inch in diameter. One tower from 

 Calcutta was five inches high and two and a half inches in diame- 

 ter ; and the average weight of twenty-two castings sent Mr. Dar- 

 win from Calcutta was an ounce and a quarter. The largest castings 

 mentioned came from the Nilgiri Hills in South India, seven thousand 

 feet above the sea, and afforded one specimen that weighed a quarter 

 of a pound, the largest convolutions of which were about an inch in 

 diameter. The manner of forming the casting is described by Mr. 

 Darwin : " A worm after swallowing earth, whether for making its 



