8 ART. 4. — N. YATSU : 



In imbedding eggs in parafin the following method was used. 

 The eggs were first thoroughly dehydrated and put in a short 

 test tube (30 mm. in length and 20 mm. in diameter) into which 

 benzine was introduced at the bottom by the aid of a fine pipette 

 and the mouth of the test tube was tightly closed with a cork 

 stopper. After about half an hour the liquid was thoroughly 

 dipped out and pare benzine was poured in. After the benzine 

 had been changed once more, finely cut paraffin was melted in 

 the tube. The latter was now allowed to remain uncorked ; 

 paraffin was put piece by piece into the mixture and a slight 

 degree of heat was applied. On cooling the tube or by slightly 

 heating the sides of the tube the entire mass could now be readily 

 removed. From this block the smallest possible portion contain- 

 ing objects may next be cut, and placed in a little paper case 

 filled with, and placed in, melted hard paraffin. A few minutes 

 after the objects had sunk to the bottom the ease was taken out 

 of the melted paraffin, and was rapidly cooled. The paper was 

 now removed, and the block was ready for cutting. In case the 

 block was not hard enough a small portion of it containing the 

 objects was again cut out, and melted with pure paraffin in another 

 paper case as just described. In some other cases I used pieces 

 of Ulva to stick eggs upon, as Hacker describes (Praxis u. 

 Theorie d. Zellen u. Befruchtungslehre p. 111). 



The embryos and larvre were imbedded by a modification of 

 the above test-tube method. When orientation was necessary, as 

 in the case of advanced larvae, the block prepared as above 

 described was examined with a low power and the desired section- 

 plane was then marked on the block. Since the larvae are 

 disc-shaped, orientation in two directions is sufficient. Sometimes, 

 after Apathy, a small piece of gelatine plate cut into a convenient 



