THE AMPHIBIA OF OKLAHOMA 



are the cytological conditions, month by month, in the ovaries of representa- 

 tive specimens of each and how do they compare? (4) How can these find- 

 ings be correlated with other factors already known to be important in the 

 initiation of breeding at different points in the breeding periods? 



Two species, Bufo cognatus Say, which has a xeric breeding pattern, 

 and Bujo woodhousii tvoodhousii Girard, which has a mixed pattern, were 

 the species chosen for study. Ninety-two females of the former from twenty- 

 three counties of Oklahoma and ninety-nine females of the latter from thirty- 

 three counties were used. The specimens of B. cognatus were collected be- 

 tween March and September; those of B. w. woodhousii, between March and 

 October. The specimens were among those in the collections of the Univer- 

 sity of Oklahoma Museum of Zoology, covering a period of ten years, alto- 

 gether representing forty-four counties; but most of these were collected by 

 Arthur N. Bragg and Charles C. Smith during 1939 and 1940. Full data 

 on all of the latter and most of the former specimens as to exact location, 

 ecological community, behavior as caught, and other matters, were at hand. 



The methods used were essentially similar to those of Fisher and Rich- 

 ards hence need not be repeated in detail. Briefly, volumetric methods were 

 utilized to determine the volumes of excised ovaries (or, in a few cases, ovu- 

 lated eggs taken from the coelom), and sections of selected ovaries were 

 prepared and stained by the usual methods. By comparing the size of the 

 individual (total length or body-volume, both of which were determined 

 for each specimen) with the volume of the ovary (or ovary plus eggs if ovu- 

 lation had occurred) the percentage of total volume represented by the ovary 

 was calculated for the month in which the specimen was collected. The 

 month by month data for the two species make specific difference evident; 

 for each species, the data may be related to the histological and cytological 

 conditions of the gonads. Ecological and other notes taken by the collectors 

 give additional bases for valid interpretations. 



We acknowledge with gratitude the aid of (1) Dr. A. I. Ortenberger 

 who permitted use of the specimens in the University Museum, (2) the li- 

 brarians of the University of North Carolina and of (3) North Carolina State 

 College for loans of literature, and (4) Dr. A. Richards who has read the 

 manuscript critically. 



Observations 



Fluctuations in ovarian volumes in the two species are presented in 

 Tables I and II. A comparison of the ovarian conditions as seen microscop- 

 ically follows: 



144 



