146 



Journal of Applied Microscopy. 



Then passed through four per cent, 

 (two days), six per cent., eight per cent., 

 ten per cent., twelve per cent., and last- 

 ly fourteen per cent., each one day. 



For hard tissues, especially woody 

 stems, it is advisable to wire the corks 

 in the bottles (two ounce saltmouth 

 are the most convenient) containing the 

 celloidin solutions, and place them in the 

 paraffin bath at 52°C. 



The celloidin deteriorates after being 

 used two or three times in the bath. 



From fourteen per cent, celloidin the 

 pieces are taken out and dropped in 

 chloroform, where they remain for four 

 to twenty-four hours, depending on the 

 size of the piece. 



The final transfer is from the chloro- 

 form to equal parts of glycerine and 

 alcohol. In this mixture the tissues seem 

 to keep indefinitely, and they can be 

 used as required. I can recommend this 

 method for class material. Very thin 

 sections can be readily cut owing to the 

 complete infiltration of the specimen. 

 F, C. HAKRISON. 



Agricultural College, Guelph. 



*The alcohol used is about ninety-four 

 per cent. It contains a little methyl 

 alcohol. 



The Use of Modeling Clay in the 

 Study of the Fish Embryo. 



In the study of the embryology of the 

 fish, the manner of growth of the germ 

 ring, and the formation of the embryo 

 from it, are difficult to demonstrate to 



Fig. 1. 



Showing complete germ ring and early 

 formation of the embryonic shield. 



the student by the ordinary drawings. 

 To overcome this difficulty, I have con- 

 structed a series of models showing em- 

 bryo. Wooden balls (at the suggestion 

 of Professor Morrill, I used croquet balls) 

 were covered with a thin layer of model- 

 ing clay, and upon this was built, with 

 the same material, models of the em- 

 bryo. The methods employed will be seen 



Fig. 2. 



Later stage in the formation of the embry- 

 onic shield. 



from the accompanying figures. The clay 

 sticks easily to the surface of the wooden 

 ball and can be made into a very thin 

 layer, which can be colored if desired. 

 Upon this are modeled the embryos of 

 various stages. I have colored the germ 



Fig. 3. 



Embryo forming, germ ring half way 



around the yolk. 



ring and embryo a deep yellow and the 

 portion inside the ring a lighter yellow, 

 while the thin layer of clay covering the 

 remainder of the ball is left uncolored. 

 Thus the uncolored area represents, in 

 this case, the periblast, the light yellow 



Fig. 4. 



Embryo nearly complete, germ ring two- 

 thirds around yolk. 



