EAETHWORM 75 



Make an outline drawing of the cross section, properly 

 oriented. This drawing should be 19 cm. in diameter. Show 

 the exact structure of a strip 2 cm. wide from the center to the 

 periphery and in addition show a portion of any other structures 

 not included in this strip. 



The foliowinfy structures should be found: cuiicula (may 

 have been removed by handling previous to sectioning) ; hupo- 

 dermis, an epithelium frequently shoAving darkly stained unicel- 

 Inhir )nucus glands; circuhv muscle layer; longitudinal muscle 

 layer. Inside the body cavity find ; the dorsal vessel with occa- 

 sionally a lateral branch, one of the parietal vessels; the intestine 

 with its fyphlosole; the nerve cord ; the ventral vessel which is 

 connected with the intestine by a membrane — the mesentery; 

 nejihridia cut in various planes ; setae or at least breaks in the 

 musculature indicating location of setae. 



IV. Study of C'uticula 



Cuticula, the delicate iridescent outer covering. Strip 

 off a piece of the cuticula from the anterior end of the body. 

 Float it on a drop of water on a slide. Apply coverglass. 



Examine prepared slide with the microscope and find : the 

 seta sacs, little sleeves within which the setae work ; the 

 nephridioporcs ; openings of the niKCus glands, numerous very 

 minutes dark spots from which fine lines radiate ; and the cover- 

 ing of sense organs. These last appear as small oval or rounded 

 areas in which no mucus openings are present. Within these 

 areas will be found groups of minute openings from which 

 sensory hairs have protruded. 



Make a diagram of a complete segment showing the rela- 

 tions of these parts as viewed under low power. 



REFERENCE 



Sedgwick, W. T. and Wilson, E. B., 1904. An Introduction to 

 General Biologv. Henrv Ilolt and Co. 



