38 



OLIGOCH.ETA 



CH^TOPODA. 



OLIGOCH^ETA. 



1. Nais proboscidea. (Low power.) Avoid too much pressure by using small slips of paper to 

 support the cover. 



Mouth; proboscis; eyes; groups of hooked ventral setae; long dorsal hair-setae; pharynx, seg- 

 ments i 4; oesophagus, segments 5 7; crop; intestine; rectum; sacs in which the setae are 

 imbedded ; muscles of setigerous sacs. (The hair-setae are first found in the 5th segment, in which 

 however they are shorter than in the succeeding.) Dorsal vessel; dilated lateral vessels placed 

 immediately in front of a septum in segments 3, 4, and 5 ; nephridia best seen in dorsal view (ist 

 nephridium in 6th segment) ; [testes in 5th segment, ovaries in 6th, atrium and opening of vas deferens 

 in segment 6 ; receptaculum seminis in segment 5 ; vesicula seminalis and ovarian sac unpaired and 

 extending some way back] ; zones of fission visible in some specimens. 



2. With a high power draw 



Brain ; body-cavity septa ; nephridium ; funnel opening of nephridium into ccelom ; tactile hairs. 



