NATURAL SELECTION 205 



(b) There was no significant correlation between the 



ability to withstand starvation and the length of 

 the embryonic period. 



(c) There was a selective death-rate in respect of the length 



of the embryonic period in the fed animals, but none 

 in the starved ones. 



(d) As regards the structural characters, there was a 



positive correlation between the length of the first 

 posterior cell and the breadth of the wing and 

 ability to survive. In two cases (breadth of wing 

 in 6* ; length of cell in $) the correlation is statis- 

 tically significant ; in the other two cases it is barely 

 significant. 



(e) As far as the difference of the means (in size) was 



concerned (comparison of survivors and eliminated), 

 it is clear that larger flies were better able to survive 

 starvation. 



Lutz notes ' discordant results as regards [reduction of] 

 variability.' The results are, on the whole, unsatisfactory — 

 e.g. in the difference between male and female. Also the 

 males which withstood starvation were distinctly more variable 

 as regards egg-larval period, but less so in the structural 

 characters. In the female the differences were insignificant. 



(11) Pearl (iQii) : observations on conspicuousness in fowls. 



Observations were made on a number of ' self-coloured ' 

 and ' barred ' fowls on a poultry farm in which they were 

 exposed to the attacks of various carnivorous enemies. Out 

 of 3,007 ' barred ' fowls 290 were killed, and out of 336 ' self- 

 coloured ' birds 35 were killed (9-6 per cent, and 10-7 per 

 cent.). Only one year's results were obtained. Pearl seems 

 to have made careful observations as to how the eliminated 

 were killed. Photographs show that, as far as the human 

 observer is concerned, the ' barred ' birds are more incon- 

 spicuous than the ' self-coloured.' He concludes that ' the 

 relative conspicuousness of the barred colour-pattern afforded 

 its possessors no great or striking protection against elimination 

 by natural enemies during a period of seven months, during 

 which they were exposed to the attacks of predators.' 



