42 HANDBOOK OF INVEETEBRATE ZOOLOGY. 



with the stomach. In a living specimen the system of 

 tubes and the cavity of the manubrium are ciliated, and 

 particles of partially-digested food may be seen circulating 

 through them. 



7. The reproductive organs: four long, crenated, opaque, 

 ribbon-like bodies (Figs. 21 and 25, I) between the inner 

 surfaces of the radiating chymiferous tubes and the sub- 

 umbrella. 



8. The ocelli: dark pigment spots, at the bases of the 

 radial tentacles. 



9. Lay a specimen open by a cut, with a sharp razor, 

 through the umbrella and the long axis of the manubrium, 

 and examine agfain in this lonofitudinal section all the struc- 

 tures which have been descril)ed. 



10. Make a drawing showing all these points. 



11. Study the manner in which the living animal 

 moves through the water, by contractions of the um- 

 brella. 



II. The more minute details of structure may most of 

 them be made out by the examination of a living specimen 

 with high powers, but it is nmch better to use preserved 

 specimens, as the active movements of the living animal 

 render careful observation difficult. If working at the 

 seashore, place a living specimen in a watch-crystal of sea- 

 water, and add fifteen or twenty drops of one per cent 

 solution of osmic acid. As soon as the specimen begins 

 to turn dark, which will be in two or three minutes, pour 

 off the water, and wash the specimen several times in fresh 

 sea- water, to get rid of all traces of the osmic acid. Stain 

 it for about half an hour in very dilute picro-carmine, and 

 then place it in a fluid composed of one-third glycerine 

 and two-thirds water, and with a sharp pair of scissors cut 

 ofi" one of the bunches of radial tentacles, and mount it 



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