26 HANDBOOK OF INVERTEBRATE ZOOLOGY. 



placing them upon a slide, examine them with a magnify- 

 ing power of 200 or 300 diameters, noticing : — 



a. Great numbers of tri-radiate spicules, formed by 

 three branches of about equal length, which meet at equal 

 angles of 120°. 



b. Long unbranched, slender, pointed, needle-like spic- 

 ules. 



c. Occasionally a second kind of tri-radiate spicule, 

 formed by the union of a short branch to the middle of a 

 lono^ branch at rio;ht ano^les. 



d. Make sketches of the spicules. 



e. Wash them thoroughly with water, to remove all 

 traces of the caustic potash, and add to the drop of water 

 which contains them a drop of acetic or sulphuric acid. 

 They soon disappear with active effervescence. 



IV. Imbed half the sponge in parafiine in position for 

 cuttino: lono-itudinal sections, and the other half for cuttings 

 transverse sections. Tolerably satisfactory sections may 

 be cut from a sponge which, after being placed for about 

 a minute on a piece of blotting-paper to absorb the alco- 

 hol, is allowed to harden in a small quantity of melted 

 paraffine ; but much more satisfactory sections may be 

 obtained in the following manner : Place the sponge in 

 absolute alcohol for about an hour and then lay it on 

 blotting-paper to absorb the alcohol, and then place it in 

 a dish large enough to hold ten or more times its volume. 

 Fill the dish with turpentine, and add all the paraffine the 

 turpentine will dissolve, and keep in a warm room for ten 

 or twelve hours. Then melt some paraffine over a water- 

 bath, and place the sponge in it, and keep it at the melt- 

 ing point for three or four hours. Fold the corners of a 

 piece of writing-paper so as to form a box about an inch 

 long, and half an inch wide and deep. Place the sponge 



