No. 4, February, 1922] GENETICS 259 



Ligowa and Gold Rain, proved highly resistant. Uruguay oat varieties were somewhat re- 

 sistant to P. coronifera, European varieties being susceptible. At the same stage of devel- 

 opment spring wheats proved more susceptible to P. triticina than winter wheats. At the 

 same stage of development maize varieties difTered in susceptibility to P. Maydis, early- 

 maturing varieties being more severely attacked than later maturing ones. The author 

 reviews various theories regarding environmental and hereditary factors which cause differ- 

 ences of reaction of varieties to parasitic fungi. — H. K. Hayes. 



1705. [Gates, R. R.] [Rev. of: Sturtevant, A. H. The North American species of 

 Drosophila. Carnegie Inst. Washington. Publ. 301. iv+150 p., 3 pi. 1921.] Nature 107: 

 743. 1921. 



1706. GoLDSCHMiDT, RiCHARD. Erblichkeitsstudlen an Schmetterlingen. III. Der Me- 

 lanismus der Nonne, Lymantria monacha L. [Genetical studies on butterflies. III. The 

 melanism of the nun, Lymantria monacha L.] Zeitschr. Indukt. Abstamm.- u. Vererb. 25: 

 89-163. PI. 6-8, 2 fig. 1921. — -Melanism in the nun moth presents in each sex an unbroken 

 series of variations from white to black, and depends upon the recombination of 3 pairs of 

 factors, 1 se.x-linked. Males are darker than females. Polymeric and sex-linked factors 

 cooperate, as in fertility in fowls (Pearl) and the silky fowl X brown leghorn (Bateson, Pun- 

 nett). — All 3 factors are dominant: A, responsible for faint pigmentation in near-white 

 individuals, but not yet fully analysed; B, spreading an increased pigmentation from the 

 middle band of the wing; C, a sex-linked darkening factor for which the female is always 

 heterozj^gous, much more intense in action than B, which it supplements. — Six forms of 

 9 and 9 of cf result from B and {CX), all visibly distinct except a few male combinations. 

 Of the theoretical 54 cross-combinations, 2S were realized, in some cases by several matings. 

 A detailed history of successive generations in 7 different stocks is given. — The unexpected 

 appearance in 4 cultures of individuals carrying the sex-linked factor (CX), although belong- 

 ing to strains free from it, is interpreted as mutation. Non-disjunction of X-chromosome 

 in the homozygous male explains 3 anomalous families, e.g., a fully melanic female, BB (CX), 

 X white cf , bb{cX) (cX), should give by "criss-cross" inheritance only white 9 9 and black 

 cfcf , but 1 brood contained, besides 55 typical individuals, 1 dark 9 , [Bh (CX)], and 1 banded 

 d', [Bb(cX) (cX)]. These 2 came from gametes b, and b(cX) (cX) of the father, meeting 

 B (CX) of the mother. — Seller reports that 28 chromosomes, including 1 remarkably large, 

 occur in both the 1st and 2nd spermatocytic mitoses. All sperms contain this number. In 

 the metaphase of the 1st maturation spindle of the egg, however, 31 chromosomes occur, of 

 which 4 fuse during the anaphase. Hence the equatorial plate of the 2nd maturation spindle 

 has only 28. But an embryo shows 62, not 56. Peculiarities of sex-linked inheritance are 

 expected from the occurrence of a compound sex chromosome. — Melanic individuals were 

 rare from 1785 till about 50 years ago, but now have largely replaced the type, especiallj' near 

 industrial centers. The theoretical statistical consequences of the appearance, within the 

 original white population, of a certain proportion of mutants for one or both of the factors, 

 followed by free intercrossing, are worked out, no selection value being attached to the melanic 

 character. In general, after a single period of mutation, dark individuals tend to become 

 more abundant than light except that, if the sex-linked (CX) is involved, the proportion 

 remains constant in the female. Repeated mutations of 10 per cent annually would be neces- 

 sary to insure supremacy of the dark form in 40 years. This percentage of mutation being 

 improbable, selection-value is ascribed to the melanic form.— Numerous measurements show 

 that dark individuals are not necessarily larger (and stronger) than the type, but artificial 

 selection of dark individuals has resulted in a marked increase in size. Disturbed natural 

 conditions around industrial districts may greatly increase a selection value elsewhere slight. 

 Possibly larvae of the melanic form better withstand the ill effects of feeding upon leaves of 

 trees covered with chemical deposits. That homozygous white males fall below expected 

 numbers in the cidtures may indicate low viability. — Melanism in the adult has no effect 

 upon the caterpillar. Melanism in the larva is due to another independent dominant factor. — 

 John H. Gerould. 



