322 NATURAL HISTORY OF OUR SHORES 



This seems a lot of trouble, but in practice it is not so. 

 It all comes in readily and easily. Then I am writing as 

 if for preparing one slide. I need scarcely explain that a 

 considerable number can be done at once, and the end 

 fully justifies the labour. The slide just described should 

 show the full structure of the sponge the canals, the 

 amoeboid, and the collared and flagellated cells, in fact, all 

 its histology. The Spicules, of course, are not well dis- 

 tinguishable in such a fine section. Coarser ones are made 

 for spicules, etc. I have given the following details as 

 regards a sponge section, but it applies, exactly the same, 

 to all soft tissues. 



If instead of osmic acid another fixative has been used, 

 say corrosive sublimate, or Bouin's Fluid, the section will be 

 white, and will require staining to bring out its details. 



In this case, when you have arrived at the stage in which 

 the wax has been washed away by turpentine, treat the 

 section to absolute alcohol by means of a dipping tube, 

 repeating this two or three times (shaking off the alcohol 

 each time). This will remove the turpentine. Now put on 

 a drop of stain, let it rest until the section is well permeated 

 (two or three minutes), wash off the loose stain with a little 

 distilled water, then drop on some strong spirit ; follow 

 this by absolute alcohol, drain off, and put on a drop of 

 oil of cloves. You will easily see when the section is clear : 

 it will become glassy-looking, uniformly all over. If any 

 opaque spots show, and refuse to clear, it has not had enough 

 absolute alcohol, so repeat this, and then oil of cloves ; 

 drain off, or rather remove the surplus oil, as already directed, 

 put on the Canada balsam, cover, and clip. 



As the slides are finished, so far, place them side by side, 

 with their clips on, in a warm place, to harden. They 

 harden most quickly near a stove, but must not get hot, 

 or the balsam will boil up, the object frizzle, and all your 

 labour be lost. 



