General Account of the Ithacan Anura. 25 



AFFINITIES OF THE EIGHT SPECIES OF ANURA IN THK ITHACAN REGION. 



The affinities of these forms have hitherto been based upon adult 

 structural characters which we consider quite as important as the 

 evidence herein adduced. But a supplementary consideration of the 

 general habits, breeding phenomena, and tadpoles of our eight species 

 reveals much of interest. 



The wood-frog (Rana sylvatica) adult easily looks to be of the R. 

 temporaria group, preferably Rana agilis. In adult habits they are 

 close parallels. In both the active pairing is brief and the males have 

 convex webbing on their hind feet. Among our eight species, the wood- 

 frog has the vitelline sphere the largest, namely 1.8 to 2.4 mm., com- 

 parable to the relatively large vitelli of R. agilis. The envelopes about 

 the vitelli of both species seem about the same size. In the wood-frog 

 tadpole the upper caudal crest extends farther forward than in the other 

 four species of Rana. In fact, it approaches the cephalic position of a 

 Hyla tadpole and seems, from a comparison of figures, to be an exact 

 duplicate of the tadpole of Rana agilis. The labial teeth formulas for 

 both are \, rarely f in R. sylvatica. This condition of tadpole teeth sets 

 the wood-frog apart from the other four frogs, which normally have f . 



In two of the remaining four frogs (Rana), the second upper row 

 of labial teeth is well developed, namely in Rana pipiens and Rana 

 palustris. The mouth-parts look like those of R. arvalis, whose sub- 

 merged egg-masses apparently resemble those of the above two forms. 

 The vitelli of Rana palustris and pipiens are from 1.6 to 1.9 mm., while 

 those of Rana arvalis are 1.5 to 2.0 mm.; the outer envelopes of the 

 two American forms may reach 6 mm. in diameter, while those of R. 

 arvalis often are 7 or 8 mm. 



The other two species of Rana, namely R. clamata and R. catesbeiana* 

 lay larger egg-complements, 3,500 to 20,000, more like Rana esculenta 

 of Europe. As in the latter, in which the vitelli are 1.5 mm. in diam- 

 eter, the eggs of these American forms are small, 1.2 to 1.7 mm. in 

 diameter. The green-frog and the bull-frog begin breeding in May or 

 later, as does the European "edible frog," and in all three there may 

 be a very extended period of breeding. The adults, of these two 

 species are the most aquatic forms in this country, as Rana esculenta is 

 in Europe. With our species the larva? regularly hibernate, while with 

 R. esculenta it often happens but is not usual. In size of tadpole and 

 labial mouth-parts, the larval characters are not unlike. 



Of the relationships of the other three Anura, little need be said. On 

 the structure of larval mouth-parts, Bufo I. americanus approaches B. 

 clamata, while Hyla versicolor approaches H . arborea. Hyla pickeringii 

 with its small goatee or third lower labial row suggests an approach 

 to the type of Bufo mouth-parts. 



*Note the suggestive parallel in late spring appearance, vocal sacs, late egg-season, 

 packet-film form of egg-complement, jelly consistency of eggs, etc., of Hyla versicolor and 

 these two Ranas. 



