AMPHIBIA 299 



Parental Care. — A number of species of frogs and toads build 

 nests in which eggs are deposited. Some frogs attach these nests to 

 leaves over the water and the tadpoles hatch and drop in. Still 

 others deposit their eggs in masses of froth some distance from the 

 water. The male sometimes proves to be the caretaker of the young. 

 In the obstetric toad he carries strings of eggs until the tadpoles are 

 ready to hatch. In another species, the South American Rhino- 

 derma, the male transfers the eggs to his huge vocal sacs until they 

 are hatched. The viviparous salamanders have already been men- 

 tioned. 



Parthenogenesis. — Bataillon, Loeb and others have induced the 

 parthenogenetic development of frogs. Parmenter's studies of the 

 chromosomes of these fatherless creatures show that they may be 

 either male or female. 



Experimental Embryology and Regeneration. — On account of 

 the convenience with which amphibian eggs may be secured inland, 

 they have been used a great deal in experimental embryology. 

 Grafting of two different species and divisions of the egg at the two- 

 cell stage have been successfully accomplished. 



W. Roux, Hertwig, Morgan, W. H. Lewis, Spemann, and many 

 other investigators have performed experiments on the developing 

 eggs of amphibia. Roux injured the first formed blastomeres, 

 and Hertwig (1893) and later Morgan (1902) studied the develop- 

 ment of half embryos and whole embryos from one of the first two 

 blastomeres of the frog's egg. W. H. Lewis first showed (1904, 

 Amer. Jour, of Anatomy, vol. 3) that the optic vesicle determines 

 location of the lens. Spemann and his students have made many 

 significant studies on the development of the eggs of Triton, the 

 salamander. (Consult Morgan, T. H., 1927, Experimental Em- 

 bryology, Columbia University Press.) 



Harrison, who was the pioneer (see page 495) in tissue culture 

 (J. Exp. Z06I., 1907, vol. 4, p. 239; 1910, vol. 9, p. 787), has trained a 

 number of anatomists, who have carried on extremely important 

 experiments on transplantation and extirpation of limbs and eyes in 

 Amphibians. An interesting account of some of the work was 

 brought out in the discussion following a lecture by Detweiler given 

 at the November, 1930, meeting of the N. Y. Neurological Society, 

 and reported in Archives of Neurology and Psychiatry, vol. 25, no. 4, 

 pp. 914-919, April 1 93 1. (Consult also papers by Harrison, Det- 

 weiler, D. Hooker, F. Swett, and R. Burns.) 



