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ordinary kinds, they are in no danger of collapsing and, as the oil 



that surrounds each embryo is not very volatile, there is no danger of 



drying. 



With a spear pointed needle, move the embryos nearly into line 



along the upper margin of the inclined plane. There is little danger 



of injuring them as the oil that 

 surrounds each causes it to 

 move moothly on the linen. 

 They may be dragged along, 

 clinging to the needle by means 

 of the oil, or they may be pu- 



shed into the position desired. 

 "When the embryo is in posi- 

 tion, raise the needle away 

 from the linen and the embryo 

 fig. i. will be left behind. 



Press the inclined portion 

 of the linen down until it adheres to the glass by the cloth side. Some 

 of the oil will run back over the embryos , so they may readily be 

 examined. Begin at one end and examine the embryos under a com- 

 pound microscope. If any are abnormal or broken, record which ones, 

 and raise the linen into its original position. When the oil has drai- 

 ned away again, remove the embryos recorded as abnormal or broken. 

 Cut a strip of tracing linen (the same kind as that described above) 

 and after being satisfied that it lies perfectly flat, rule the glazed side 

 with a needle. Each line is a little depression and can be easily seen. 

 It may be ruled with a soft lead pencil if so desired. I have found it 

 convenient to use strips about a centimeter wide and three centimeters 

 long, cut diagonally at one end, fig. 4, so that a glance will show 

 whether the strip is right side up or not, and marked with the index 

 number of the embryos to be imbedded. Great care should be taken 

 to get the strip absolutely flat, if good straight ribbons are desired. 



Spread the glazed side of the strip of linen, the same side that 

 has been ruled, with a collodion mixture such as is used in fixing sec- 

 tions to slides. This should be kept in stock. It is made by dissolving 

 celloidin in equal parts of absolute alcohol and ether, until the solu- 

 tion will run only slowly, and adding to it an equal part of oil of clo- 

 ves. When they are well mixed the solution is ready for use. 



After the strip is spread with this mixture the excess should be 

 removed. The amount that should be left depends on the size of the 

 objects that are to be placed. If they are about the size of starfish 

 embryos, draw the strip between the thumb and finger. If they are 

 very small, this process will need to be repeated two or three times. 

 If a thicker film is needed, it may be obtained by catching the strip 

 by one end and drawing it over a knife edge. It will be necessary 



