THE AMPHIBIA OF OKLAHOMA 



bufos and ranas" of Oklahoma, M. c. olivacea, H. v. versicolor, and typically 

 S. hurterli and S. couchii. To the second belong S. bombijrons, S. hammondii , 

 Ps. diir^ii, Ps. triseriata and probably Ps. strecl^eri as well. Since females of 

 Acris crepitans lay their eggs singly or in small masses (Smith, 1934), this 

 species should also be classified with the second group. In general, those 

 species which attach their eggs in a definite arrangement to submerged vege- 

 tation belong to the second group. Ps. clarf^ii is especially interesting from 

 this view point. The eggs are laid in very small masses, ten to twenty or so 

 in a bunch, attached to grasses or sedge leaves (sometimes to weeds and other 

 such objects) and placed just beneath the water surface, almost never more 

 than three inches below it, irrespective of the depth of the water. I have never 

 observed the actual laying of the eggs in nature but I have found pools in 

 which hundreds of such small masses of eggs could be seen after a large 

 breeding congress. Since the egg complements of the females are invariably 

 large (in round numbers about 1,000; Bragg, 1943b, 1943c), it follows that 

 the mated pairs must move about during egg deposition, depositing these 

 small groups of eggs here and there on the vegetation. Ps. strecl{eri ( Bragg, 

 1942) and S. hurteri'i (Bragg, 1944a) also lay eggs near the surface of the 

 water attached in irregular masses to vegetation. Both of these, however, 

 merely crawl about in a limited area as the eggs come, much as paired toads 

 do on the bottom, rather than move definitely from one place to another 

 after the manner of Ps. clarkji. S. bombifrons has similar habits but typically 

 attaches its eggs deeper in the water. In very shallow pools, however, S. bom- 

 bifrons may lay its eggs in small masses widely scattered, ( Bragg, 1941, 1943). 

 In one case, such a small mass hatched six out of only seven eggs that had 

 been laid. S. hurterii also sometimes scatters small bunches of eggs about. 



(5) Tadpole Development. 



The most striking thing in tadpole development in Oklahoma is the 

 marked variation in developmental rates manifested at different times and 

 places. Two factors are operative here, one of which is entirely environmental, 

 the other protoplasmic. The principal environmental factor is temperature, 

 low temperatures retarding development markedly, and high temperatures, 

 within physiological limits, greatly speeding the process. The protoplasmic 

 factors are not well understood but their effects are perfectly obvious where 

 developmental rates differ in a single pool, as is often the case. An example 

 of this follows. 



The pool chosen for illustration had been formed during heavy rains 

 by a road which, serving as a dam, had backed water into the oak-hickory 

 woodland forming a muddy pool of about one-half acre in extent which 

 varied in different parts of it from a few inches to about three feet in depth 

 (Fig. 30). During and immediately after the rains the following species were 

 found breeding here: Bujo t. americanus, Hyla v. versicolor, Pseudacris 

 streckeri, Microhyla c. olivacea, Scaphiopus hurterii, and Rana berhindieri. 

 Later, other breeding congresses of some of these species occurred here antl, 

 •' R. berhindieri is a possible exception. See Bragg ( l'H4). 



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