432 ANNUAL EEPOKT SMITHSONIAN INSTITUTION, 1912. 



developed into adult toads at the advent of the reproductive 

 period. The progeny resultmg from these toads, in which the 

 metamorphic changes had been delayed, underwent metamorphosis 

 within the usual normal time. They therefore had failed to inherit 

 the varying developmental process. It required the combination 

 of all the above-mentioned factors to produce a sexually fertile 

 toad larva (fig. 9, 6d). Then' progeny (6C), although produced by 

 the mating of the unique sexually fertile female larva with an ordi- 

 nary completely developed mate, for years did not progress beyond 

 the stage with developed hind legs and displayed little metamorphic 

 energy. 



Secondly, the independence of water, which is already expressed 

 in the normal reproduction of the midwife toad, by the phases 

 passed over out of water durmg development was pushed to the limit. 

 If one hastens all the processes of development by the employment 

 of warmth and retards the hatching by withdrawing light and placing 

 them in comparatively dry surroundings, then one obtains gigantic 

 eggs (fig. 9, 3a), in which the embryos remain until they have well- 

 developed hind legs (3&). The toads developed from these are 

 dwarfed and eggs laid by them are of lesser numbers than m the nor- 

 mal toad, and possess from the very beginning a great amount of 

 yolk, much more than in the usual eggs, and it is a curious sight to 

 see a dwarfed male perform his brooding function with the very 

 large few eggs. If one continued to apply the same stimuli to the 

 eggs, then one agam obtained larvje, with completely developed hind 

 legs (3Z>) ; but if one transferred them into normal conditions as far 

 as requirements of temperature, light, and moisture are concerned, 

 larvae were obtamed, which at hatchmg possessed bud-like hind legs 

 (3C). 



Thirdly, one can develop the larvse to the two-legged stage, away 

 from water, simply on moist ground; in this, if danger of death 

 threatens, one must return them to their normal element. The land 

 larvse (fig. 9, detail fig. 5) possess a thicker skm than the aquatic 

 larv£e, which is easily observed by the fact that in the aquatic larvae 

 only (comp. fig. 9, 2c) the rump musculature is visible through the 

 skin. The land larvse possess also a narrower fin, but are stronger 

 in the bones and musculature of the tail. The lungs are subjected 

 to a curious modification in the aquatic larvse; they are sunple, 

 smooth- walled tubes (2(Z) ; m land larvse of the same age they have 

 already been separated into lobules, alveoli, and sacs (5a), which 

 approach, both in form and structure, those of the completed toad 

 {2E). The toads developed from terrestrial larvse are dwarfed. If 

 one keeps the larva produced by these again out of water, then the 

 al)ility to exist out of water is mcreased. A further stage (5C) is 

 therefore reached than in the preceding generation, which extends to 



