BIRDS AND EVOLUTION 379 



accessory ankle callosity has not become hereditary, and also 

 why the median callosity, though unused, continues to 

 appear generation after generation." It is no reproach to 

 say that this is purely speculative biology — only it remains 

 unconvincing. 



A number of experiments have been made on different 

 kinds of animals as to the effect on the progeny when the 

 parents are liberally treated with alcohol. The results are 

 rather discrepant ; the alcoholisation seems to be very 

 deleterious in some cases, e.g. guinea-pigs, but not so in 

 other cases, e.g. fowls. The experiments made by Raymond 

 Pearl (191 7) showed relatively little bad effect in poultry. 

 He used pure-bred Black Hamburg cocks and pure-bred 

 Plymouth Rock hens, which were subjected to vapour of 

 ethyl-alcohol, methyl-alcohol, or ether in inhalation tanks, 

 the treatment extending over an hour each day, for 130-354 

 days, with a mean of about seven months. The full brothers 

 and sisters of the " treated " birds were used as controls. 



The results show that " the treated animals are not 

 conspicuously worse or better than their untreated control 

 sisters or brothers. The survivors, i.e. those not killed by 

 accident, after roughly a year and a half of daily treatment, 

 are becoming a bit too fat for their best physiological economy, 

 but except for that point, and the reduced activity which 

 goes with it, they are very much like normal fowls." At the 

 end of the experiments the treated hens were on the average 

 9*9 per cent, heavier than their untreated sisters. 



In a subsequent paper. Pearl states that after alcoholic 

 treatment of the parent fowls : the pre-natal mortality of the 

 embryos was reduced ; the post-natal mortality of the 

 chicks was reduced ; the sex-ratio was not sensibly affected ; 

 there was no significant difference in mean hatching weight 

 when only the male parent was treated ; the offspring of 

 alcoholised parents showed a mean hatching weight and a 

 mean adult weight higher than that of normal birds ; the 

 proportion of abnormal chicks was not greater than usual ; 

 many germ-cells of the alcoholised parents did not form 

 zygotes (fertilised ova), but those that did were not defective 



