EXPLANATION OF PLATES. 



Except where otherwise stated the following figures have been made with a 

 2mm. apochromatic immersion objective and a 4 projection eyepiece with a 

 camera extention of 37 inches and a magnification of 1,500. The slides, except 

 where otherwise mentioned, were prepared by Mr. Elwood Mendenhall in the 

 Earlham Biological Laboratory. The ascaris slides were stained by the iron- 

 haematoxylin method. The material was fixed in Fleming's chrom-osmium- 

 acetic fixative. The time of exposure was from 2 to 10 seconds. Zettnow's filter 

 was used in each case, and for the Lilium candidum sections which were stained 

 with saff"ranin, a Methylene blue filter in addition. No ground glass was used in 

 any instance. 



4— A. OF Science. (49) 



