ANNUAL OVARIAN CYCLE 



The ovaries were then dissected and a fine-meshed copper basket was 

 used to suspend each in alcohol in a graduate burette of 25 c.c. volume and 

 calibration of 0.1 c.c. Readings were taken as before, allowance being made 

 for the volume of the basket. All measurements were recorded in cubic milli- 

 meters. The ovarian volume in percentage of the volume of the entire body 

 was estimated and recorded with the number of the frog, date of its collec- 

 tion, body length, volume of the entire body, and volume of the ovaries. The 

 average percentage of ovarian volume to total volume of the specimens fixed 

 during each month was figured, as shown in Table I. As noted before, all 

 months are represented in the collections, although the collections of Jan- 

 uary consist of only a few females whose ovaries had been removed and em- 

 bedded in paraffin previous to this part of the study; no data are available, 

 therefore, on the size of the ovaries for specimens fixed during this month. 

 Collecting during January is usually difficult because of low temperatures. 



Observations on the shape, color, and general features of the ovaries 

 were made at the time of their removal. Notes were taken on all unusual 

 specimens, and in some few cases the gonads were left intact for further ob- 

 servation. With the aid of a dissecting microscope a careful study of all ex- 

 ternal features of the ovaries was made, with especial attention to the changes 

 occurring in their appearance from month to month. 



Representative ovaries from each month were embedded in paraffin, 

 sectioned at eight micra, and stained with Heidenhain's iron-hemotoxylin. 



OBSERVATIONS 



Ovarian Volume 



The calculation of the volumes of the ovaries relative to the volumes of 

 the entire bodies of the frogs, given in percentages (the percentage of ovarian 

 volume), shows a significant variation during the year. (See Table I.) Frogs 

 collected in September have a low average of ovarian volumetric percentage 

 and the variation among individuals is slight. The average percentage for 

 frogs of October collections is lower than any since March, and the decline 

 of average percentages continues through December. As stated previously, 

 no frogs of January were available for measurement of their ovaries. The 

 average for February continues low and the variation among individuals 

 is not noteworthy. A small decrease in the average percentage was found in 

 the frogs collected during March. The range of percentages among individ- 

 uals here is wider, however. A distinct rise was noted in the average percent- 

 age of volume for frogs fixed in April, and a still greater individual variation 

 was evident. The average percentage for frogs of May is the highest of the year, 

 both among Bouin-fixed specimens and formalin-fixed frogs. The June average 

 remains high, although it is slightly less than that of May. The July average 

 is also among the highest of the year. It is interesting to note that the average 

 for this month was lowered by a group of frogs collected during the drouth 

 year of 1936, which suggests a probable effect of rainfall and humidity on the 



