III.] THE EARTHWORM. 253 



region ot the body, but further details concerning 

 them may be left till later. 



/ The perivisceral fluid. Take a fireshly killed worm 

 and remove a small portion of the dorsal body- 

 wall. Insert the point of a capillar}- tube and draw 

 off a little of the perivisceral fluid. Examine at 

 once under a high power, and note — 



a. The water}' serum, in which float colourless 

 vacuolated amaboid corpuscles. 



^. "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. 



I. Pin :he 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 >\-ithin 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. T\i^ p/iaryriXy 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 tibres which attach it to the 

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

 secting), give it a roughened appearance when 

 viewed from above. 



