VERMES 153 



caught by seeking them with a lantern at night when they 

 roam about. They can easily be kept for months in a box 

 of rich earth occasionally moistened and supplied with 

 decaying leaves. A wire netting should be tacked over the 

 top. In order to kill them properly for dissection, they 

 should be placed in a jar or dish a foot in diameter and cov- 

 ered with water to which thirty cubic centimeters (one 

 ounce) of alcohol is to be added every forty or fifty minutes 



FlG. 180. Forepart of an earthworm with the left body-wall removed ; a, dorsal 

 blood vessel; 6, brain ; c, crop ; d, opening of the male reproductive organs ; 

 g, gizzard ; i, intestine ; k, kidney ; m, mouth ; , one of the ganglia of the nerve 

 cord ; oe, esophagus ; p, pharynx ; r, receptacles for sperm cells ; ov, ovary ; ovd, ' 

 duct from ovary ; v, ventral blood vessel. Drawing by W. H. Reese. 



until they become unconscious. They are then best pre- 

 served in seventy per cent alcohol. 



Each of the segments or somites numbering about one 

 hundred and fifty bears four pairs of short bristles (setce) 

 by means of which the worm holds itself so firmly in the 

 burrow when one attempts to dislodge it. The swollen 

 band between the thirtieth and fortieth somites is the 

 clitellum, from which exudes a sticky substance used to 

 construct the egg band. This encircling band after being 

 hardened by the air is worked forward and as it passes the 

 fourteenth or fifteenth segments receives the eggs there 

 extruded by two minute apertures not visible to the naked 



