EARTHWORM 91 



teen to sixteen), gizzard (seventeen to ninteen), stomach- 

 intestine extending to the posterior end of the body. In 

 the walls of the esophagus in somites ten to twelve are 

 three pairs of small sacs or pouches, the calciferous glands, 

 which open into the esophagus. 



Compare the several organs in size, color, thickness of 

 walls, the lining of each. In the stomach-intestine note 

 the dorsal infolding, the typhlosole. Note also the delicate 

 muscle fibers w y hich extend from the body wall to the pharynx. 

 What possible function might these serve? 



4. Excretory System. This consists of paired segmental 

 organs, the kidneys or nephridia, which are made up of coiled 

 tubes held closely together and suspended close to the 

 ventral and lateral body wall. Remove one of the nephridia, 

 place on a slide, and examine with the compound micro- 

 scope. 



Make a large drawing and in it show all the internal 

 structures that you have observed. 



5. Nervous System. Dissect and remove the anterior 

 end of the alimentary canal except the pharynx. This will 

 expose the white nerve cord, lying in the median ventral side 

 of the body cavity. Immediately over this is the ventral 

 bloodvessel, one of the main longitudinal trunks of the 

 circulatory system. 



Examine with the lens and notice that there are small 

 swellings, the ganglia. How many in each somite? Are 

 there nerves coming out from the cord? How many in 

 each somite? Do they come from the ganglia, or from be- 

 tween the ganglia? Carefully expose the cord anteriorly, 

 pushing the pharynx to one side, and on the dorsal side of 

 the pharynx will be found the cerebral ganglia or brain. 

 How is this connected with the ventral cord? Make a 

 large drawing of the brain and several of the ganglia and 

 their nerves. 



