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 2 3-2 5 

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

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



