1914] Sharp: Diplodinium ecaudatum 57 



oil the operator can by means of the mechanical stage bring a desired 

 animal up to the end of the glass tube into which it may be sucked by 

 a slight twist of the piston of the syringe. In this way the desired 

 animals may be sorted out free from dirt and other animals to the 

 number of from two hundred and fifty to five hundred in a single tube. 

 By substituting a fresh slide on which is placed a drop of Canada bal- 

 sam or styrax the animals may be easily ejected from the glass tube into 

 the mounting substance. 



By mounting these animals between two thin cover glasses and then 

 fixing the cover glasses in a brass frame which is constructed to hold 

 them as a window frame holds the pane of glass, the same individual 

 animal may be viewed from either side. This simple bit of apparatus 

 has proved itself exceedingly useful in determining many otherwise 

 difficult problems and is therefore recommended for consideration to 

 those making similar investigations. 



Sectioning. — When it is desired to section the animals they are 

 segregated by the above method and ejected from the glass tube into 

 small gelatin capsules (such as may be obtained at any pharmacy) 

 which have been partially filled with imbedding paraffin. The capsule 

 is placed in a warm oven at the proper temperature, the paraffin melts, 

 the cedar oil diffuses through the paraffin, and the animals sink to the 

 bottom. By soaking in water for a few minutes the gelatin capsule 

 may be easily slipped off and by cutting off the bottom end each time 

 and running this through another paraffin filled capsule for at least 

 four times, a paraffin infiltration of the organisms, sufficient to allow 

 of sectioning, is obtained. When the infiltration is complete the lower 

 four or five drops of paraffin containing the animals are withdrawn by 

 means of a warm capillary pipette and run into a mould which has 

 been prepared in the following manner. A small brass rod is filed to a 

 square cross section and fitted in an imbedding plate so that when the 

 paraffin is poured around it, it will act as a core. When the paraffin 

 hardens and the core is removed a perfect mould is obtained. Paraffin 

 of a much higher melting point should be used for the moulds than 

 that which is used for imbedding, and if the paraffin of the mould be 

 slightly tinted by Sudan III., the liability of cutting into the imbed- 

 ding paraffin is eliminated. When the imbedding paraffin containing 

 the animals is run into the mould care should be taken that the animals 

 are well distributed through the paraffin and that the paraffin is just 

 above the melting point. It then hardens before the animals have time 

 to sink to the bottom, and so results in their remaining well distributed 



