MEXICAN TAILLESS AMPHIBIANS 79 



The following account of the life history of this species has been 

 published by Doctor Noble : ^^ 



The species of Eupemphix which both Mr. Breder and Doctor Chapin have stud- 

 ied, is the wide-spread pustulosus. It has the peculiar shoulder girdle characteristic 

 of the genus and of Paludicola. Breder made his observations in Darien, Panama, 

 during February, March, and April, 1924. Most of his breeding pairs he found 

 during the second and third week of March. E. pustulosus lays its eggs in a 

 foamy mass which floats so lightly on the water that it does not break the surface 

 film. No less than thirty-six nests were studied criticallj' by Breder. The nests 

 were usually at the water's edge, generally floating but adhering to any adjacent 

 object. The few "nests" that were not in contact with the water had probably 

 been left stranded as the water in the pool receded during a drought. Sometimes 

 the "nests" were partly and, rarely, completely hidden by leaves. The eggs 

 developed normally whether or not the mass was in contact with the water. Doc- 

 tor Chapin found E. pustulosus breeding at Tapia, Canal Zone, August 7, 1923, in 

 circular basins of cement placed around the bases of trees to protect them from leaf- 

 cutting ants and kept filled by rain water. The egg masses were 

 laid on the edges of this basin exactly as in the case when larger 

 bodies of water were utilized. Other egg masses were found in 

 small stagnant pools near by or even in hoof marks which had 

 become filled with water. 



The eggs of E. pustulosus are practically identical with those 



of P. fuscomaculata, being only 1.4 mm. in diameter, unpigmented 



and laid in large numbers. Development, however, is slower than 



in the latter species and many details which Budgett tells us are 



"blurred and, as it were, hurried over" in P. fuscomaculata are ' ,' 



accentuated in E. pustulosus. In both species the yolk is small, ^ 



but obviously dense, for the embryo soon curves around it in- Figure 18.— Head 



stead of incorporating it at once into the body as in our common ° , "''^* omopa 



pustulosus (U. 

 frogs and toads. The adhesive organs, which Bles found to arise g j^ j^ -^^ 



separately in Paludicola, differentiate in Eupemphix from a cres- 47124) from 



cent as in less specialized frogs {Scaphiopus, etc.). The external Santo Domingo, 



gills, which remain small in the first genus, soon develop extraor- Oa^aca, Mexico: 



dinary proportions in the latter. The nasal pits differentiate j' dorsal view 



in the latter at the apex of the head and are not visible from the 



ventral surface as in the case of the former. In short, practically every larval 



feature other than general body form differs in Paludicola and Eupemphix during 



the early stages. 



Here again as in the pelobatids and ranids mentioned above the early larval 



stages may show great differences when the other life history features are very 



similar. In the case of Eupemphix and Paludicola the differences, however, are 



not due merely to the different stage at which the frontal organ cells begin to 



secrete their liquifying fluids, a change in the growth rate of the whole or a part 



of the Eupemphix embryo must have occurred to produce the large gills and other 



distinctive features of the early larva. Nevertheless, the place of egg deposition, 



the form of the egg mass and egg-capsules, the structure of the mature larvae and 



the general breeding habits are much aUke and conform to our conclusions that 



the genera are closely related. 



" Noble, G. K., Ttie value of life history data in the study of the evolution of the Amphibia. Ann. 

 New York Acad. Sci., vol 30, pp. 87, 88, Oct. 31, 1927, 



