29'2 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



VII. Gills. — Examine one of the gills about the 

 middle of the series. Note its attachment to the body 

 wall, its basal webbing, the main trunks and their 

 branches. Remove the gill to a slide and examine it 

 under a low power to see the mode of branching and the 

 blood-vessels. Note the small size and simple character 

 of the first gill. 



VIII. Setae. — Notopodial setae may be easily obtained 

 from a dissected specimen by taking hold with the forceps 

 of the inner end of the setal sac and drawing it inwards. 

 In this way the whole bundle of notopodial setae will be 

 removed. To clean off the tissues of the setal sac and any 

 adhering strands of muscle the preparation may be 

 warmed in 5 per cent, caustic soda. After washing in 

 water the setae may be placed in glycerine for a time and 

 then permanently mounted in glycerine jelly. Only 

 unworn setae should be selected for examination. 



By treatment of an excised neuropodium with warm 

 caustic soda the muscles become gradually softened, and 

 by the. aid of a pair of needles may eventually be separated 

 into an anterior and a posterior mass, between which the 

 chaetae lie. With care the entire band of neuropodial 

 chaetae may be obtained. It should then be washed in 

 water, placed for a time in glycerine and mounted in 

 glycerine jelly. The various stages of formation of the 

 new chaetae at the ventral end of the series may be seen. 

 There are usually two or three fully developed crotchets 

 which have not yet come into use. These should be 

 selected for observation of their characters as they are 

 uninjured by wear. 



I have found it very useful to have dissections 

 of small specimens, 17 to 50 mm. long, for the study 

 of young nephridia (which are too small to be easily 

 removed from the body wall), gonads, blood-vessels, &c. 



