ITT.] THE EARTHWORM. 253 



region of the body, but further details concerning 

 them may be left till later. 



/ The perivisceral fluid. Take a freshly killed worm 

 and remove a small portion of the dorsal body- 

 wall. Insert the point of a capillary tube and draw 

 off a little of the perivisceral fluid. Examine at 

 once under a high power, and note — 



a. The watery serum, in which float colourless 

 vacuolated amceboid corpuscles. 



(8. Watch the corpuscles. Aggregates of them fre- 

 quently fuse on exposure, prior to disintegration. 



y. Take a second drop of the fluid and treat with 

 acetic acid and magenta. The nuclei of the 

 corpuscles alone stain deeply. 



D. The alimentary organs. 



1. Pin the worm down as before and open it up dor- 

 sally. Remove the seminal vesicles and work out in 

 order — 



a. The buccal sac, a thin-walled sac lying within the 

 first 2 — 3 segments. Muscular fibres pass from its 

 anterior end to the body-wall. The aperture of 

 the mouth can be seen through its transparent 

 roof. 



b. The pharynx, a spacious thick- walled structure, ex- 

 tending back to the sixth segment. It is tied 

 down to the body-wall by a fan-shaped series of 

 muscular fibres. ^- 



The cut ends of those fibres which attach it to the 

 dorsal surface of the body-wall (removed in dis- 

 secting), give it a roughened appearance when 

 viewed from above. 



