PRESIDENTIAL ADDRESS SECTION D. 93 



It will now be well to consider Lamarckism, including the 

 belief in the inheritance of acquired characters, from modern 

 aspects. 



The hypothesis of the inheritance of acquired characters is 

 championed in Britain by MacBride. Early this year he published 

 an interesting review on the subject in "Science Progress." This 

 hypothesis implies that changes in habit and environment produce 

 an effect, not only on the animals directly exposed to them, but 

 also on their offspring. The changes produced by an altered 

 environment are an expression of the response or reaction of the 

 animal in its endeavour to adapt itself to changed circumstances. 

 By the inheritance of acquired characters is meant the inheritance 

 of the effects of use and disuse. We may note some of the inter- 

 esting researches, many of them experimental, published recently 

 in support of this hypothesis. 



Kammerer working in Vienna has carried out a series of 

 experiments chiefly on Amphibia. One set of experiments was on 

 European salamanders. The yellow salamander, S. maculosa, 

 inhabits the lowlands and gives rise to 30 to 40 gilled young. The 

 black salamander, S. atra, lives at high altitudes and gives birth 

 to only two young. The gilled young of S. maculosa 

 live in water for six weeks before losing their gills and changing 

 into the land form. The young of S. atra are born as terrestrial 

 animals, ready to take up the mode of life of the parent. How- 

 ever, if a pregnant black salamander is opened, at least a dozen 

 embryos are found Inside, but only two embryos are destined to 

 survive, for the others degenerate to form a fluid that serves to 

 nourish the two. The two lucky embryos possess long gills, but 

 these gills are absorbed before birth. According to MacBride,. 

 Kammerer asserts that "if S. atra be graduallv accustomed to live 

 under warmer and moister conditions she will begin to produce 

 first three and ultimately four young at a birth, that these youn? 

 will enter the world at an abnormally early period of development 

 — even before the gills are fully absorbed ; that if these young be 

 reared to maturity under the same conditions they will give rise to 

 still more young at a birth, and these young will be provided 

 with gills, and will take to the water — in a word, that S. atra can 

 be induced to assume the habits of S. maculosa, and that these 

 habits will be transmitted to posterity." Kammerer has also per- 

 formed the reverse experiment. He finds that if S. maculosa, is 

 subjected to increasing cold and drvness, it produces fewer at a 

 birth, and these are born in a more advanced state of development. 

 In three generations only three or four are born at one birth, their 

 gills are mere stumps, the gill clefts are closed, and the animals 

 can live on land. S. maculosa has apparently acquired the habits 

 of S. atra. 



Kammerer has also experimented with the midwife toad, 

 Alytes obstetricans. Alvtes differs from other toads in that it pairs 

 on land, and the male does not develop a horny pad on the hand. 

 The eggs are larger and fewer in number than in the case of 

 ordinary toads. The male carries the fertilised eg^-strings round 



