68 LABORATORY DIRECTIONS 



III. STUDY OF PREPARED SLIDES 



Under the microscope examine cross sections of the body 

 in the region of the intestine. Make an outline drawing of the 

 cross section, properly oriented. This drawing should be 18 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 following structures should be found: cuticula (may 

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

 mis, an epithelium frequently showing darkly stained unicellular 

 mucus glands; circular muscle layer; longitudinal muscle layer. 

 Inside the body cavity find : the dorsal vessel with occasionally a 

 lateral branch, one of the parietal vessels; the intestine with its 

 typhlosole; the nerve cord; the ventral vessel which is connected 

 with the intestine by a membrane the mesentery; nephridia cut 

 in various planes ; setae or at least breaks in the musculature in- 

 dicating location of setae. 



IV. STUDY OF CUTICULA 



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. Ex- 

 amine prepared slide with the microscope and find : the seta sacs, 

 little sleeves within which the setae work ; the nephridial pores; 

 openings of the mucus glands, numerous very minute dark spots 

 from which fine lines radiate; and the covering 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 pro- 

 truded. Make a diagram of a complete segment showing the 

 relations of these parts as viewed under low power. 



REFERENCE 



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

 General Biology. Henry Holt and Co. 



