324 Relation of Use and Disuse to Evolution 



by the environment are ever parallel in parent and offspring. 

 Examples of such parallel inductions are seen when plants 

 are stunted by unfavorable living conditions, with the result 

 that their seeds are exceptionally small. The next genera- 

 tion then starts out with an original handicap of a low food 

 reserve. In some animals it has been possible to handicap 

 the offspring by exposing the parents to extreme cold, or 

 to injurious chemical action. Such parallel inductions, 

 however, fail to establish the transmission of acquired 

 characters. 



An Austrian, Paul Kammerer, published the results of 

 experiments with black and spotted salamanders, in which 

 he believed to have demonstrated the transmission of modifi- 

 cations. These animals differ somewhat in their habitats, 

 the former being an alpine form and the latter occupying 

 lower regions. In both species the eggs develop within the 

 body of the mother, the development proceeding farther 

 before birth in the black salamander. By transposing the 

 living conditions, Kammerer succeeded in modifying the 

 breeding habits of the animals, and the modification in- 

 creased progressively for several generations. From these 

 results Kammerer argued the cumulative transmission of 

 modificatioijs; but biologists generally, however, are not 

 convinced by the evidence, for this type of alteration in 

 habit is well known among plants and animals, and is usually 

 reversible through a further reversal in conditions. Other 

 experiments by Kammerer had to do with enlarging the yel- 

 low area at the expense of the black, in the spotted sala- 

 mander, by keeping the animals (that is, the parents) in a 

 yellow box. Aside from the short duration of these ex- 

 periments, and the small numbers of animals employed, 

 there is the serious defect that there were no pedigree or 

 quantitative studies to determine the normal range of fluc- 

 tuation in the yellow spots. These experiments appear to 

 be convincing in proportion to one's preconceived bias to- 

 ward or away from the general doctrine of the transmission 

 of the effects induced by the environment. 



