H ARDESTY, Spinal Net^ves of the Frog. 331 



to the adjoining square, a ring was made at the ^spot where the 

 image of the fiber would fall on the paper, instead of a dot. 

 Since there were seldom more than 1 5 fibers in a square, the 

 occurrence of border fibers of this kind was not so very fre- 

 quent and this simple method of dealing with them proved 

 highly efficient. 



When all the squares had been counted and recorded on 

 a sheet of paper, the sheet, for identification, was marked with 

 the same label as that of the slide. 



The numbers in the squares could now be added at any 

 time, the sum total being the number of fibers contained in 

 the section. 



Only medullated fibers or those stained by osmic acid were 

 counted. By the use of osmic acid for this purpose, sections 

 were secured in which doubtful cases as to whether a structure 

 was a medullated fiber or not, were fortunately rare, and the 

 counts made either by the photographic or the net method 

 proved highly satisfactory. 



The net method as here employed, avoids any form of 

 auto-suggestion which might give rise to error, for the observer 

 never knows what number he has obtained for a given section 

 until the numbers in the individual squares have been added, 

 and this may be postponed until all the sections from a given 

 nerve have been counted. The results obtained for the different 

 specimens were neither tabulated nor compared till after all the 

 counts had been made. 



V. The General Results of the Counting. 



The 6th. spinal nerve of one side was taken from each of 

 seventeen specimens. These were killed during the months of 

 January, April, June, September and October, and ranged be- 

 tween 4.7 grams and 78.8 grams. In this locality at least, 

 Rana virescens rarely attains a weight exceeding 80 grams after 

 the ovaries have been removed ; and the largest are always 

 female. 



In the colder months, animals under the normal conditions 

 of winter could not be secured, but had to be chosen instead 



