THE AMPHIBIA OF OKLAHOMA 



sis in the white mouse and discussed features similar to those found in am- 

 phibian forms, particularly the appearance and behavior of the nucleoli just 

 previous to the period of maturation in the ova. Clark (1934) followed the 

 annual cycle in the California sardine, Sardina caendea, and determined the 

 time of maturity in the female by measuring the diameters of ovarian ova at 

 various seasons of the year. 



Notes on the life history of Acris are found in the papers of Dickerson 

 (1908), Wright and Wright (1933), Wright (1932), and Stejneger and 

 Barbour (1933). Numerous investigators have reported within very recent 

 years the efifect of rainfall, temperature, humidity, periods of light and dark- 

 ness, and hormonal products on the annual sex cycles of animals. 



Material and Methods 



The cricket frog, Acris crepitans, common throughout a large part of 

 the United States, is one of the few non-hibernating frogs and toads, and may 

 be found in central Oklahoma during all months of the year. According to 

 Wright (1932), this frog at breeding has the least size of any, with the excep- 

 tion of individuals of Pseudacris ocularis; males mature at a length of 15-29 

 mm. and females at 16-33 mm. 



All observations reported in this paper were made on fixed specimens. 

 Those frogs upon which the study was largely based were collected during 

 the years, 1931-1939, principally from the vicinity of Norman, Oklahoma.^ 

 At the time of collection, ventral incisions were made in the specimens, they 

 were fixed in Bouin's fixative, and stored in 70 per cent alcohol. Females in 

 the collections number 108 individuals, and collections from all months are 

 represented. In addition, specimens of Acris in the Museum of Zoology of 

 the University of Oklahoma were available for supplementary study. These 

 had been fixed in a 10 per cent solution of formaldehyde and preserved in 70 

 per cent alcohol. Seventy-one female frogs are included in this collection and 

 represent the months of March, May, June, July, August, and October, from 

 the years 1924 through 1933. Only frogs of mature size were used, specimens 

 smaller than 16 mm. not being considered. It was not found that the method 

 of fixation made any noteworthy difference in the measurements of the speci- 

 mens or ovaries. 



Several methods of study were employed. The first consisted of a meas- 

 urement of the entire volume of the body of each of the 179 females, and the 

 dissection and measurement of the volume of their ovaries. From these data 

 the ratio of the ovarian volume to that of the entire body for each frog was 

 estimated. Volume of the body was determined by suspending the specimen 

 by a fine wire hook in alcohol in a 100 cc. graduated cylinder with calibration 

 of 1 cc. Readings were taken while the frog was suspended therein and after 

 its removal, and the difference calculated to give the volume, allowance being 

 made for the volume of the hook. 



' 'Ihc work (if Miss Whaley, previously incntioncd. upon the males of this species 

 was also based on animals collected in this vicinity. They were mistakenly identiticd as 

 A. gryllus. 



