EARTHWORM. 



LUMBRICUS SP. 



PLACE the worm in the dissecting pan with enough- 

 water to cover it. What is the form of the body? Does 

 it vary in any part? What is the color? Does it vary? 

 Has the body any protective covering? Are there append- 

 ages such as legs? Are there gills or other respiratory struc- 

 tures? Are there organs of hearing or sight? 



I. External Anatomy. 



1. General Features. Notice the regular segmentation 

 of the body into a series of rings, somites or metameres. 

 How many? Compare with the number found on other 

 specimens and indicate whether it is constant. Are the 

 somites of the same size and form throughout? Notice 

 the prostomium projecting from the first somite, and the 

 clitellum or girdle about one-third of the way back from the 

 anterior end. Which segments make up the clitellum? 

 In what way does this part of the body differ from the rest? 

 The clitellum is composed of glands in the skin which secrete 

 a substance to form the cocoon or case in which the eggs 

 are deposited. 



2. Regions of the Body. Distinguish an anterior or head 

 end, and a posterior or tail end. Is there a definite head? 

 How are the dorsal and ventral sides differentiated? Are 



