EFFECTS OF CHANGED ENVIRONMENT 215 



Fresh Experiments. — Among the twentieth century experi- 

 ments on the transmission of modifications, there are a few 

 which suggest that a dogmatic denial of the possibility is very 

 unwise. As a striking instance let us take Kammerer's experi- 

 ments on salamanders. 



(a) The common yellow and black salamander (Salamandra macu- 

 losa) is either viviparous, producing a large number of larvae 25-30 

 mm. in length with four limbs and short gills, or ovo- viviparous, lay- 

 ing large eggs which hatch out immediately into similar larvae 23-25 

 mm. in length. After a few months of larval life in the water they 

 undergo metamorphosis into land-salamanders 45-56 mm. in length. 



(b) The black Alpine salamander (Salamandra atra) produces at a 

 birth two fully formed terrestrial young ones 38-40 mm. in length, 

 the larval stage being skipped — in obvious relation to the Alpine 

 conditions of life., 



(c) Kammerer kept the spotted salamander in the cold and got it, 

 after a few pregnancies, to produce only two young ones, as in the 

 black salamander. 



(d) He kept the black salamander in a warm place with plenty of 

 water, and got it to produce 3-9 gilled larvae, thus approaching the 

 condition in the spotted salamander. 



(e) Now the offspring of the salamanders thus treated (c and d) were 

 kept for two and a half years in a vivarium, but did not become 

 sexually mature until they were placed in the open in conditions 

 normal to 5. maculosa. They became mature when three and a 

 half years old. 



The offspring of (c) gave birth to (1 ) very advanced larvae, 45 mm. 

 long with much reduced gills, metamorphosing several days after, or 

 moderately advanced larvae, 20 mm. long, with large gills; or (2) 

 to small larvae 26 mm. long with rudimentary gills, laid on land, 

 and metamorphosing after four weeks into salamanders 29 mm. in 

 length. Thus there was a partial persistence of a modified mode of 

 reproduction in the absence of the modifying conditions . 



(/) The offspring of (d) bore in the water 3-5 larvae, 33-40 mm. 

 or 21-23 mm. in length, light in colour, and possessing gills. In 

 this case there was practically a continuance of the modifying con- 

 ditions and there was an augmentation of the parental modification. 



The difficulties in regard to these very interesting experiments 

 are: (1) they do not deal with a structural modification in the 

 ordinary sense ; (2) it may be that the experimental conditions of 



