544. Mr. C. F. M. Swynnerton on 



the flavours vary immensely. Thus, Robin, Nightingale, 

 and Swallow are beastly. But the white eggs of the Little 

 Eittern are as sweet and mild as cream, nor are the eggs of 

 the Barn-Owl much inferior to them.'' And in his second 

 letter he refers to the well-known strong odour of Petrels' 

 eggs — "but, is it deterrent?" 



If Petrels' eggs are by any chance of low-grade edibility — 

 and this, in the last resort, can only be ascertained by experi- 

 ment, as Mr. Wallis actually suggests it should be — I would 

 imagine that the smell is likely to be useful for aiding in 

 their recognition by enemies rather than deterrent in itself; 

 just as many of the smells of insects are probably mnemonic, 

 like their appearance, rather than directly deterrent. The 

 real deterrent quality is usually something more deep-seated 

 than appearance, smell, or taste, but difl'erences in it, both 

 of degree and kind, are commonly accompanied by differ- 

 ences, strong or slight, of taste and (to other mammals than 

 man) smell ; and it is on this account that the observations 

 I have quoted are exceedingly interesting and suggestive. 

 They amplify greatly the common knowledge that eggs vary 

 in flavour, and extend it to raw eggs. It does not necessarily 

 follow, of course, that flavours and smells that are agreeable 

 to us are always associated with great digestibility in relation 

 to natural enemies. Danaida chrysipjms, one of the most 

 nauseous of butterflies in its effects, has a mild and not 

 unpleasant nutty flavour, while members of the unpleasant 

 genus MyJothris smell sweetly of menthol and sweet-briar. 

 Nor does it follow that an object which we find wholesome 

 when cooked is necessarily as digestible to its other enemies 

 when raw. Monticola is greatly disliked by my cat, which 

 refuses to eat it even when specially starved. Yet, toasted 

 through (feathers and all), he has readily eaten it to 

 repletion-point, 



Mr. Wallis goes on: "Although the Little Bittern lays 

 in an uncovered, or slightly covered, nest, I have not chanced 

 on any sucked eggs, whilst the covered nest of the Water- 

 Rail is, in my experience, exceedingly liable to be raided by 



I 



