Other Invertebrate- Animal Study 463 



An earthworm has a peculiar, crawling movement. Unlike the snake, 

 which also moves without legs, it has no scales to function in part as legs; 

 but it has a very special provision for locomotion. On the under side of a 

 worm are found numerous setae tiny, bristlelike projections. These will 

 be seen to be in double rows on each segment, excepting the first three and 

 the last. The setae turn so that they point in the opposite direction from 

 which the worm is moving. It is this use of these clinging bristles, 

 together with strong muscles, which enables a worm to hold tightly to its 

 burrow when bird or man attempts its removal. A piece of round elastic 

 furnishes an excellent example of contraction and extension, such as the 

 earthworm exhibits. Under the skin of the worm are two sets of muscles ; 

 the outer passing in circular direction around the body, the inner running 

 lengthwise. The movement of these may be easily seen in a good-sized, 

 living specimen. The body is lengthened by the contraction of circular 

 and the extension of longitudinal muscles, and shortened by the opposite 

 movement. 



The number of .segments may vary with the age of the worm. In the 

 immature, the clitellum, a thick, whitish ring near the end, is absent. 

 The laying of the earthworm's egg is an interesting performance. A sac- 

 like ring is formed about the body in the region of the clitellum. This 

 girdle is gradually worked forward and, as it is cast over the head, the sac- 

 ends snap together enclosing the eggs. These capsules, yellowish-brown, 

 football-shaped, about the size of a grain of wheat, may be found in May 

 or June about manure piles or under stones. 



Earthworms are completely deaf, although sensitive to vibration. 

 They have no eyes, but can distinguish between light and darkness. The 

 power of smell is feeble. The sense of taste is well developed ; the sense of 

 touch is very acute; and we are not so sure as is Dr. Jordan, that the 

 angleworm is at ease on the hook. 



Any garden furnishes good examples of the home of the earthworm. 

 The burrows are made straight down at first, then wind about irregularly. 

 Usually they are about one or two feet deep, but may reach even eight 

 feet. The burrow terminates generally in an enlargement where one or 

 several worms pass the winter. Toward the surface, the burrow is lined 

 with a thin layer of fine, dark colored earth, voided by the worm. This 

 creature is an excavator and builder of no mean ability. The towerlike 

 "castings" so characteristic of the earthworm, are formed with excreted 

 earth. Using the tail as a trowel, it places earth, now on one side and 

 now on the other. In this work, of course, the tail protrudes; in the 

 search for food, the head is out. A worm, then, must make its home, 

 narrow as it is, with a view to being able to turn in it. 



An earthworm will bury itself in loose earth in two or three minutes, 

 and in compact soil, in fifteen minutes. Pupils should be able to make 

 these observations easily either in the terrarium or in the garden. 



In plugging the mouths of their burrows, earthworms show something 

 that seems like intelligence. Triangular leaves are invariably drawn in 

 by the apex, pine-needles by the common base, the manner varying with 

 the shape of the leaf. They do not drag in a leaf by the footstalk, unless 

 its basal part is as narrow as the apex. The mouth of the burrow may be 

 Jined with leaves for several inches. 



The burrows are not found in dry ground nor in loose sand. The 

 earthworm lives in the finer, moderately wet soils. It must have moisture 



