Inheritance of Acquired Characters. 95 



The parallel induction in germ andsoma is believed to be brought 

 about by " altering the nature of the metabolic products included in 

 the living protoplasm." That such effects are transmitted for one 

 or two generations is an excellent example of a cytoplasmic effect 

 temporarily inherited, and indicates that minimal quantities of such 

 substances are multiplied so as to produce a powerful effect. 

 Kammerer claims to have obtained such a result in experiments 

 with a lizard, where the character white instead of red belly, 

 impressed by high temperature, was transmitted through the sperm 

 to the next generation of adults. 



The experiments of Kammerer (1909, 1919) with Alytes 

 obstetricans have been much discussed. His recent results are 

 largely confirmatory of earlier papers published ten years ago, and 

 a number of other contributions, including an elaborate series of 

 experiments with salamanders, have appeared in the intervening 

 years. It is well-known that Alytes differs from other European 

 Anura in that its strings of eggs are not laid in the water, 1 but are 

 twisted round the legs of the male and carried for some time during 

 their stages of embryonic development. Their bearer only resorts 

 to the water when they are ready to hatch as advanced tadpoles 

 having a single pair of gills covered by an operculum. 



When these animals are kept at a higher temperature (25? 

 30 C.) with access to water, the eggs are laid in the water, and they 

 hatch earlier, when the gills are still exposed. If these conditions 

 are continued, so that the animals are obliged to breed in the water, 

 by the F 4 generation the tadpoles will have three pairs of gills as 

 in other frogs. A number of other interesting changes occur. 

 The eggs of Alytes are much larger and less numerous than in other 

 frogs and toads. Thus, Rana produces 600-4,000 eggs with a 

 diameter of only 1-7 mm, while in Alytes the number of eggs is 

 about 60 and they are 3-5-4 mm. in diameter owing to a great 

 amount of yolk. Developing in the water, the eggs of Alytes 

 become rapidly smaller in successive generations. 



But perhaps the most critical of these results concerns the 

 secondary sexual characters of the male. Here again Alytes differs 

 from other Anura in the absence of the characteristic horny padwhich 

 developes on the thumb or wrist of the male during the breeding 

 season, enabling him to retain his hold on the female while in the 

 water. When pairing and egg-laying occur in the water, however, 

 according to Kammerer this pad gradually appears in Alytes, until 



1 It is an interesting fact that in one locality, Miinster in Westphalia 

 (Kammerer, 1909, p. 452), the eggs are normally laid in water. 



