201 Major R. F. Meiidejolin on the [Ibis, 



the fraud, and hence deduces that they can distinguish 

 strange eggs — a curious contradiction ! He is also, by the 

 way, responsible for the story that, according to the evidence 

 of a Kaufmann Kiessel, a Cuckoo at St. Johanu on the Saar 

 incubated two of its own eggs and reared the young — a 

 statement Rey rightly refuses to accept. 



Kiinz then advanced the startling idea that the eggs in 

 the nest of the foster-parent produce such an effect on the 

 female Cuckoo that she lays an e^g of the same colour ! 



Rey and Wasnam enunciated the theory, already discussed 

 under '^Egg-coloration," that the food supplied to the 

 young Cuckoos by their different foster-parents influences 

 the subsequent colour of the eggs they lay. They argue 

 that, in certain more or less restricted areas, as distinct 

 from whole countries or wide expanses, the resemblance of 

 the Cuckoo's egg to those of the foster-parents is an almost 

 invariable rule ; in other localities it frequently occurs, while 

 in others again it is quite the exception, and this latter is 

 especially the case near large towns, where the original 

 distribution of birds has been interfered with by the pro- 

 gress of civilization, resulting in many species becoming 

 rarer or ceasing to breed there. As a consequence of this, 

 the Cuckoo is unable to find a sufficient number of the 

 nests she prefers and has to use others. 



Hence it follows that, if a female Cuckoo lays eggs of 

 the same type all her life, there will be an insufficiency, in 

 such localities, of the nests she requires, and thus eggs of, 

 say, the Whitethroat type will be found in nests of the 

 Red-backed Shrike, etc. Dr. Rey then draws the conclusion 

 that the more exclusively the Cuckoo entrusts her eggs to 

 any one species the greater is their similarity, and, con- 

 versely, the greater the number of species selected by 

 diff^erent females the less is the resemblance. 



Rey also agrees w^ith Baldamus that, when possible, the 

 Cuckoo deposits its eggs in the nest of that species by 

 which it was reared, and that consequently a resemblance in 

 egg-coloration results from the repeated rearing of many 

 generations by the same foster-parents. If, then, as he 



