334 ORILLA STOTLER WERNER. 



changes of pure. paraffin to remove all the wintergreen. They 

 were then placed in an oven tor twelve hours, then in fresh pure 

 paraffin for one half hour and finally embedded. While the 

 tissues were being passed through the paraffin, the temperature 

 was kept just so the paraffins would stay liquid, care being taken 

 not to raise it above this point. Sections were then cut about 

 five and one half micra. I think, however, that it would be 

 better to cut them thicker than this, say about seven or eight 

 micra. In this way many more cells could be found with none 

 of the chromosomes sectioned away. 



After the tissues were mounted the work was completed ac- 

 cording to the usual methods. 



The chromosomes in these cells stand out clear and beautiful. 



The destaining is a delicate process and must be done with 

 extreme care. No definite time can be given for the iron alum in 

 destaining for the time depends upon the thickness of the sec- 

 tions, the concentration of stain used, etc. Experience alone 

 brings the desired results. The work is best done under the low 

 power of the microscope (loX ocular and 2/3 objective). 



Technique for Testis Smears. These were prepared just as the 

 sections but the oils and the paraffins were omitted. From the 

 40 per cent, alcohol they were passed successively down through 

 the grades of alcohol, care being taken to gradually lower the 

 temperature of the fluids until when the work is completed they 

 are at room temperature. This can best be accomplished by 

 placing all the containers on an electric embedding plate. 



The study of the avian chromosomes has presented difficulties 

 in that the chromosomes are easily massed together, making a 

 count difficult or impossible. With the technique here employed 

 this difficulty has to a considerable degree been avoided. 



Approximately six hundred cells were examined. The greater 

 portion of these were soma cells from the tissues of nine individ- 

 uals. In determining the number of chromosomes I have, in 

 most cases, made drawings from several different slides. How- 

 ever, where the cells were found particularly clear and distinct I 

 have made several drawings from the same slide. 



The chromosomes were measured in the following manner. A 

 separate camera lucida drawing was made of each. A thread 



