Vererbung, Variation, Mutation. ^n'ö 



Vererbung, Variation, Mutation. 



797) Doncaster, L., Chromosomes, heredity and Sex: a review of the 

 present state of the evidence with regard to the material basis of 

 hereditary transmission and sex-determinaton. In: Quart. Journ. Micr. 

 Science, Bd. 59, Nr. 4, S. 487—521, 1914. 



A review of recent work on the relation between chromosomes and inheri- 

 tance of Mendelian characters, and between chromosomes and sex-determination. 

 In favour of the belief that chromosomes are concerned with the transmission 

 of Mendelian factors are mentioned (l) the behaviour of the chromosomes in the 

 maturation divisions of the germ-cells, (2) the phenomena of gametic coupling, 

 (3) the observations of Federley, Baltzer, Herbst etc. connecting chromoso- 

 mes with jnherited characters. Objections to this belief are discussed. In con- 

 nexion wifti sex, the evidence is arranged under (l) the behaviour of hetero- and 

 idio-chromosomes, especially in Insects with bisexual and parthenogenetic repro- 

 duction, and in Nematodes; (2) the facts of sex-limited inheritance. It is con- 

 cluded that the arguments for a relation between the behaviour of chromosomes 

 and Mendelian segregation are by themselves strong but not indisputable ; that 

 the arguments connecting chromosomes with sex are stronger, and that the facts 

 of sex-limited inheritance strongly reinforce both conclusions. It is considered, 

 however, that sex is not determined simply by the presence or absence of a sex- 

 factor, but by a type of metabolism induced by the presence or absence of cer- 

 tain chromosomes, and that it is possible that the same type of metabolism may 

 perhaps be induced by other causes. The article includes a short description of 

 a new case of an unpaired chromosome in the female, in a strain of Abraxas 

 grossulariata. Some eggs contain 27 chromosomes after maturation, others 28. 



Autoreferat. 



798) Castle, W. E., Pure Lines and Selection. In: Journ. of Heredity, Vol.V, 

 Nr. 3, S. 93—97, 1914. 



The author points out tat "pure line" to the stock breeder means a race of 

 animals bred as closely as possible to a recognised Standard. To the biologist a 

 "pure line" is an imaginary thing and is only possible by breeding together ani- 

 mals which are identical in their heredity. The pure line theory rests upon two 

 postulates: (l) that the effects of environment are not inherited, (2) that inheri- 

 ted characteristics do not vary. The second postulate is the one which at pre- 

 sent is a much disputed qüestion. The author maintains that while the idea of 

 gametic purity is no longer held in its original form, the concept of purity has 

 been shifted from the characters which can be seen to vary to factors which 

 may be imagined to be invariably, though they cannot be seen. In experimental 

 work he considers that there is no conclusive evidence of the constancy of cha- 

 racters or for the ineffectiveness of selection within pure lines. Particular refe- 

 rence is made to the work of Johannsen, Jennings and the Hagedoorns. 

 In answer to the statement made by the Hagedoorns that "if selection really 

 might change genetic factors, modification of any character would be as easy in 

 one direction as in another", Castle states that a series of selection experiments 

 with the hooded pattern of spotted rats shows that plus selection and minus se- 

 lection are both effective and that selections away from and back to any modal 

 condition of the pattern are equally easy of accomplishment. Pearl. 



799) Yule, G. V., Fluctuations of sampling in Mendelian Ratios. In: 

 Proc. Camb. Philosoph. Soc, Bd. XVn, Nr. 5, S. 425—432, 1914. 



