198 SCIENCE PROGRESS. 



2. Psilura 7nonacha L. S and do. ab. eremita O. ? . 

 In 1893 Standfuss raised a brood from a pair of normal 

 P. ?nonacha received from Silesia. This brood contained 

 one female specimen of the dark aberration eremita, which 

 was paired with a normal P. monacha $ from Zurich. The 

 issue consisted of 22 (2 $ and 20 ? ) typical monacha, 23 

 (18 $ and 5 ?) typical eremita, and 6 forms (5 $ and 

 1 ? ) in which the characters of the two are unsymmetrically 

 mixed, not harmoniously blended. There is no apparent 

 tendency to hermaphroditism. This unsymmetrical mixture 

 resembles that occasionally seen in the male of Ocneria 

 disfiar L., where also, according to Standfuss, the patches 

 of the female pattern that sometimes appear do not betoken 

 organic hermaphroditism. 



3. P. eremita $ and P. monacha ? . This was a 

 natural pairing found by Standfuss in Silesia. The result 

 was entirely different from that of the former cross, inas- 

 much as the issue contained every kind of transition be- 

 tween the two parent forms, while a few even transcended 

 the male parent in darkness. 



Thus the two specimens of so-called e7'emita in this and 

 the former observation, though externally so much alike, 

 possessed entirely different properties in regard to the 

 power of transmission to descendants. Standfuss explains 

 the apparent contradiction thus : The first eremita was a 

 true sport or aberration, and in its case the rule held good 

 as usual. The second, also called "eremita" (which did 

 not show the eremita characters so well as some of its own 

 offspring), was a link in the chain leading by slight varia- 

 tions to a darker and presumably better protected form of 

 P. monacha, which, under the influence of natural selection, 

 is gradually developing itself in certain parts of the range 



of 195 individuals are known for three generations, seems, like that of 

 Aglia tau and its aberration lugens {infra, p. 199), to promise suitable data 

 for the verification of Mr. Francis Galton's law of heredity. According 

 to this law the sum of the ancestral contributions is expressed by the series 

 (°*5) + (°*5) 2 + (°'5) 3 + • • • (o'5) n . each term standing for a generation. 

 See Galton, Natural Inheritance, 1889, p. 134, and " Average Contribution 

 of each Several Ancestor to the Total Heritage of the Offspring," Proc> 

 Roy. Soc, 1897, pp. 401-413. 



