A Clear Rule Wanted. 55 



should have another lot of different eggs, say, six to 

 add to our differentiated cuckoos, and, following the 

 same reasoning applied to all sHght differences, we 

 should have at least another half-dozen, thus bringing 

 the number of known different egg-laying cuckoos up 

 to at least nearly thirty. It would be a benefit if the 

 supporters of the theory of different cuckoos for each 

 different egg would tell us at what point of difference 

 you have assurance of the fixed and definite ma- 

 ternity, so to speak. Some such rule of principle is 

 much needed. Do the various fly-spots and different 

 distribution of fly-spots (for in some cases they are 

 freely and almost equally scattered at one end, and in 

 others drawn into a sort of faint ring between the end 

 of the egg and the part where it begins to contract), 

 each trace themselves to definite cuckoos ; or at what 

 point does the process end ? We know perfectly 

 well that when closely looked at there is no case in 

 which any birds' eggs are exactly alike, and that 

 sometimes the eggs of one clutch — more especially of 

 certain birds — will so markedly differ from each other 

 as to spots and arrangement of spots as to look rather 

 a motley group ; and if in the case of the cuckoo no 

 variety is to be allowed to the female here, we want 

 to have some clear rule about it. We know nothing 

 definite about what determines these differences, but 

 our point here is, that if you go the whole hog, as 

 you ought to do, about your different egg-laying 

 cuckoos, you foist on the individual layers a uni- 

 formity such as is found in no other bird — a thing 

 adding another mystery to the mysteries about the 

 cuckoo and its eggs. 



In case of any dispute, here are Dr. Bowdler 

 Sharpe's own words : 



