FACTS OF INHERITANCE 165 



atra) produces at birth two fully formed terrestrial 

 young 38-40 mm. in length. 



(c) Kammerer kept S. maculosa in the cold, 

 and got it, after a few pregnancies, to produce only 

 two young ones, as in S. atra. 



{d) He kept S. atra in a warm place with plenty 

 of water, and got it to produce 3-9 aquatic larvae, 

 thus approaching the condition in S. maculosa. 



(e) The offspring of the Salamanders thus 

 treated (c and d), became sexually mature when 

 three and a half years old in conditions normal 

 to S. maculosa. The offspring of (c) gave birth 

 (1) to very advanced larvae, 45 mm. long with 

 much-reduced gills, metamorphosing several days 

 after, or moderately advanced aquatic larvae 

 40 mm. long, with large gills ; or (2) to small 

 larvae, 20 mm. long, with rudimentary gills, laid 

 on land, and metamorphosing after four weeks 

 into salamanders 29 mm. long. Thus there was 

 a partial persistence of a modified mode of re- 

 production 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. Thus there was 

 an augmentation of the parental modification 

 {d) in conditions which resembled those of the 

 original experiment. 



The difficulties in regard to this very interesting 

 set of experiments are : (1) they do not deal 

 with a structural modification ; (2) it is possible 

 that the experimental conditions acted directly 

 on the germ-cells in (c) and (d) ; (3) there was 

 some measure of artificiality in the conditions 

 under which the second generation developed, 



