66 INVERTEBRATE ZOOLOGY. 



experiments by drawings showing (1) Isolated spicules, (2) Relation of spicules 

 to each other. Include in the examination the spicules about the osculum. 



1 9, Mount a small piece temporarily in 70 %. Add a drop of HCl at 

 edge of cover and watch result through microscope. Of what are the spi- 

 cules composed ? 



Type II.— A Sycon Sponge. 



20. Study a specimen (or small group) as in 1. Do not cut open with 

 scissors, but use a razor or a sharp scalpel. Divide the sponge longitudinally, 

 and make a few cross sections of one longitudinal half. Examine all these 

 in the watch crystal. If you succeed in obtaining a very thin cross section, 

 make a temporary mount of it and examine. 60''. Note the thick walls, the 

 narrow central chamber and the pores in its walls. What do these signify ? 

 Does an examination of the sections of the walls solve this problem ? Have 

 these pores any regiilar order ? Note the palisade of large spicules about the 

 osculum. 



2 I . Repeat 4 for spicviles. 



22. '^tiidy of prepared sections. Method and introduction. The walls 

 of this specimen are too thick to be moiinted whole as in 2. and we must 

 resort to microtome sections. The two most useful are longitudinal and 

 transverse sections. 



[For this purpose specimens are prepared as follows : 



(1) Borax Carmine, 36 hours and thus stained in toto. 



(2) Washed out in '' acidulated alcohol." i. e. 70 ^ + a few drops of HCl, un- 

 til bright scarlet, 8-5 minutes. 



(3) 95 »/— 3-6 hours. 



(4) 100^— 3-6 hours. 



(5) Turpentine— 3-6 hoiirs. 



(6) In parafflne, in oven, 1-2 hours and imbedded.] 



Consider the form of the specimen and answer the following :— Will one 

 sponge yield more transverse or more longitudinal sections ? Which set will 

 vary more among themselves V Will all longitudinal sections include the 

 lumen V Longitudinal sections lying in the plane of a radius of a transverse 

 section are termed radial, those not including a radius, but merely parallel to 

 a tangential plane, are termed tangential. How many of each sort? Are 

 all radial sections the same y Are all tangential sections '? If the longitiidi- 

 nal axis of a specimen curves, how will that complicate the sections? What 

 sort of specimens should be selected for sectioning ? 



