202 PROBLEMS OF GENETICS 



duced for inspection it will, I think be time to examine the evi- 

 dence for the inheritance of acquired characters more seriously. 

 I wrote to Dr. Kammerer in July, 1910, asking him for the loan 

 of such a specimen 13 and on visiting the Biologische Versuchsan- 

 stalt in September of the same year I made the same request, but 

 hitherto none has been produced. In matters of this kind much 

 generally depends on interpretations made at the time of ob- 

 servation; here, however, is an example which could readily 

 be attested by preserved material. I notice with some surprise 

 that in a later publication on the same subject no reference to the 

 development of these structures is made (see below) . 



The statements here given represent but a small part of 

 Kammerer's papers on the subject. He gives much further 

 information as to the course of the experiments, especially in 

 regard to the fate of the eggs laid on land and the aberrations 

 induced in them by treatment. The ramifications of the ex- 

 periments are, however, very difficult to follow, and as I am not 

 sure that I have always understood them I must refer the reader 

 to the original. 



More recently Kammerer has published 14 a most curious 

 account of experiments in crossing his modified and abnormal 

 Alytes, derived from the water-eggs, with normal individuals. 



In the first case the cross was made between a normal female 

 and an abnormal male. The offspring were normal in their 

 habits. In the next generation bred from these almost exactly 

 a quarter showed the abnormal instinct. 



The reciprocal cross was made between an abnormal female 

 and a normal male. In this case the offspring were abnormal in 

 their behaviour; but the second generation bred from them 

 showed three quarters abnormal and one quarter normal. 



Certain details as to numbers and sexes of the various families 

 bred in the course of this amazing experiment are given in a 



13 In reply to my letter Dr. Kammerer who was then away from home very 

 kindly replied that he was not quite sure whether he had killed specimens of Alytes 

 with " Brnnftschwielen " or whether he only had living males of the fourth genera- 

 tion, but that he would send illustrative material. 



14 Kammerer, P., Natur, 12 December, 1909, Heft 6, p. 95, repeated in 12 

 Fhigschrift d. Detilsch Ges. f. Zuchtungskunde, Berlin, 1910. 



