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I. Cut along the middle line from the 25th to the 40th segment, and after fixing 

 the skin at each side, examine the Hood vessels. Make a diagram shewing, 

 in a side-view, the dorsal, sub-intestinal, latero-neural, and sub-neural trunks, 

 and the lateral branches connecting the dorsal with the sub-intestinal, and 

 the dorsal and sub-intestinal with the sub-neural. Eemove the worm 

 from the salt solution and continue the incision along the middle line. 

 (a) Collect and examine (high power) the perivisceral fluid, noting and 



drawing the granular amceboid corpuscles. 

 (6) Cut across the dorsal vessel and examine the blood (high power), 

 noting and drawing the small oval colourless blood corpuscles. 



(c) Strip off a small portion of the cuticle from the middle line of the 



back and examine (high power), noting the row of comparatively 

 large dorsal pores, and the extremely small canals scattered 

 irregularly over the surface, and the fine lines which cause the 

 iridescence. 



(d) Examine the setse from various segments (low power), noting and 



drawing the modified forms in the region of the clitellum, and in the 

 10th, 15th, and 23d segments. 



J. Examine a prepared transverse section of earthworm — 

 1. With low power ; note and draw — 



(1) The body wall consisting of (a) the structureless cuticle, (b) the epi- 



dermis, (c) a pigmented circular muscular layer, (d) a longitudinal 

 muscular layer divided by the setae into four broad and four extremely 

 narrow bands, (e) the parietal layer of coelomic epithelium. 



(2) A mesentery (if present) extending between the body wall and the 



intestine. 



(3) The alimentary canal, indicating (a) the pigmented visceral layer of 



the coelomic epithelium, (6) the longitudinal muscular layer, (c) the 

 circular muscular layer, (d) the typhlosole and its blood vessel, (e) the 

 dorsal and sub-intestinal blood vessels, and the lateral vessels if pre- 

 sent, 

 (i) The nerve cord, and the three vessels in connection with it. 



(5) The setae (two lateral and two ventral on each side), the muscles ex- 



tending from their inner ends to the body wall, and the setigerous 

 glands between the muscular bands. 



(6) The segmental organs and their apertures internal or external to the 



ventral seta?. 

 2; With high power ; draw a portion to show — 



(1) The nucleated cells of the epidermis. 



(2) Circular and longitudinal muscular fibres of the body wall and intestine. 



(3) The long granular cells of the visceral layer of the coelomic epithelium 



and the ciliated nucleated cells of the intestinal epithelium. 



(4) The muscular fibres and epithelium of the mesentry, if visible. 



(5) The nerve cord which consists of (a) a muscular sheath, in connection 



with which are three large fibres, (b) nerve fibres, especially abun- 

 dant in the centre and on the dorsal aspect, and of (c) ganglionic cells, 

 which in the ganglia occupy the ventral surface and sides. 



Advanced students may further examine the epithelium covering the various organs 

 and lining the body cavity, and the blood vessels in preparations, made from 

 the tissues of a fresh earthworm, treated with J p.c. solution of silver nitrate, 

 and mounted in glycerine. 



