162 ' HANDBOOK OF INVERTEBRATE ZOOLOGY. 



3. The female reproductive orifice is on the median 

 line, between the thirty-third and thirty-fourth annuli. 



4. A nearly square region, formed by the thickening 

 of the ventral portions of the thirty -ninth, fortieth, and 

 forty-first annuli, and pierced by two pairs of fine pores, 

 the external openings of the mucous glands. 



5. The external apertures of the segmented organs, 

 With a hand-lens two small papillae may be seen pro- 

 jecting backwards from the posterior margin of every 

 fifth annulus; one on each side, near the edges of the 

 ventral surface. The openings are upon the posterior 

 annulus of each somite, that is, the annulus just in front 

 of the one which has a pigment spot upon its dorsal 

 surface. 



6. Make a drawing of the ventral surface, to show all 

 these points. 



II. Internal Structure. 



Specimens for dissection may be killed with chloroform, 

 and preserved in seventy-five per cent alcohol. A day 

 or two before they are to be dissected, they should be 

 placed in water, to soften them. 



Cut through the integument, along the middle of the 

 dorsal surface, from the second or third annulus to the 

 last but one. With a pair of fine forceps lift up one edge 

 of the integument, near the middle of the bod}-, and Avith 

 a pair of fine-pointed scissors cut the blood-vessels, mus- 

 cles, and connective tissue which bind it to the upper sur- 

 face of the digestive tract. Pin the flap of skin down 

 on to a flat piece of cork or a wax tablet, under water, 

 and then free the opposite edge, and pin it out in the 

 same way. Work forwards and backwards from these 

 two pins, pinning down the integument at short interval-. 

 If this is carefully done, the whole digestive tract will 

 now be exposed in place. 



