THE EARTHWORM 



289 



cavity, the aelome, through which a smaller tube, the digestive 

 tract, extends from end to end of the body. The coelome is 

 divided throughout, except in its most anterior region, by vertical 

 partitions, the septa, which extend inward from the body wall to 

 the digestive tract, thus holding the tract in position Uke so many 

 transverse mesenteries. The nervous system consists of a ventral 



Fig. 139. — Median sections of anterior end of earthworm. 



Above, diagrammatic representation with parts labeled. 



Below, the same as shown by a model. 



br, brain; c.y., calciferous gland; cr, crop; e, esophagus; g, gizzard; m, mouth; .t.c, 

 ventral nerve cord; ph, pharynx; s, seta. 



(The upper figure is redrawn with modifications from Marshall and Hurst, "Practical 

 Zoology," copyright, 1895, by John Murray, printed by permission. The lower figure is 

 from a photograph of the Jewell model of the earthworm, by courtesy of the General Hio- 

 logical Supply House, Chicago, 111.) 



nerve cord (Fig. 139) on the inner surface of the body wall and 

 composed of right and left parts which separate anteriorly where 

 they encircle the esophagus, to unite in the pair of cerebral gan- 

 glia, or brain, which lies dorsally in the third segment. There are 

 nerves passing outward from the cord and brain as in higher 

 animals. In each segment, except a few at the extreme anterior 

 end, there is a pair of excretory organs, the nephridia, each con- 

 .sisting of a tubule having at one end an opening into the coelome 



