INVERTEBRATE ZOOLOGY. 65 



(6) Lay it down, preparation side up, and alloir to dry. 



(7) Place then a drop of Canada Balsam in the center of a clean slide. i)ivert 

 the cover glass and place it upon the drop. 



I 4. Scrape the inside of the cheek very slightly with a dull knife and 

 mount a little of the substance obtained in a drop of clear saliva — 100'. The 

 field will be filled with large flat cells that look like thin membranes. Find 

 one that is isolated from the rest and well spread out. Place this under 

 300-600'. In the center will be seen its nucleus, a clear oval mass. Surround- 

 ing this \\ill be seen numerous round dots, highlj' refractive. These are ball- 

 bacteria. Make a permanent mount of this as given above [13]. 



PORIFERA. 

 Type I.— An Ascon Sponge. 



I 5. Place an entire sijecimen. or group of several, in a watch crystal of 

 70^ and study under dissecting microscope. Notice manner of gro\\i:h. main 

 body with osculum, and lateral buds. Have any of these oscula? Cut open 

 with scissors and notice main cavity. Have the lateral buds ca^'ities? Do 

 they communicate with the main chamber V The texture of the sponge re- 

 sembles felt. Cause of this ? Draw the group with above details expressed. 



I 6. Place a portion of the wall (single thickness) in a solid watch glass 

 of Borax Carmine. Cover it and leave an hour. [While waiting, condiict ex- 

 periments 17-19 and then return.] Wash out in 70^?. 5-10 minutes. Then five 

 minutes each in 95 ^ — 100^ — turpentine — and place in a drop of Balsam on a 

 slide, inner irall iipjierniost . cover and examine. Most superficially come the 

 endodermal cells, which in life are like collared monads. Bj- fociissing a lit- 

 tle deeper the spicules come in view, and deeper yet the irregular cells of the 

 mesoderm. Certain of these are very large — spherical and deeph' stained. 

 These are either eggs (one large cell) or spermatozoa (a mass of cells). Draw 

 these details. 



I 7. Select another portion of the wall, spread it out on a dry slide, inner 

 wall uppei-most, and allow to dry. When perfectly dry. examine for spicules, 

 50-60 J. 



I 8. Place a few i)ieces in a watch crystal of K-O-H. and heat gently 

 over an alcohol lamp. Pipette the residuum ujion a slide, cover and examine. 

 50-60''. Compare with dried specimen. Exjiress the results of the last two 



