190 ]\r aj or E. F. Meiklejolin on Me [Ibis, 



sistecl, and there seems fairly conclusive evidence to show 

 that the existence or lack o£ suitable deserted nests has no 

 bearing on the matter. 



Similarly, amongst such species as deposit their eggs on 

 the ground or on rocks, with little pretence at nest-making, 

 one finds individual cases where a more or less compact nest 

 has been made, and the building instinct has persisted. 



It may perhaps be argued from this that the loss of the 

 '' building instinct '^ is a very gradual process, or even that, 

 on the contrary, in the species in question a gradual evolu- 

 tion towards nest-building is taking place, and it would be 

 interesting to have reliable data as to whether the number 

 of individuals using the deserted nests of other birds was on 

 tlie increase or decrease. 



The next link would appear to be the loss of the -incu- 

 bating iustinct as evidenced in some exotic species, which 

 leave their eggs to be hatched mainly or entirely by the 

 heat of the sun. 



Here, again, the question arises as to M'hether it is correct 

 to speak of the loss of the incubating instinct, since, if birds 

 be descended from reptiles, those leaving their eggs to l;e 

 hatched by the sun, and indeed those building no nests, 

 have remained most true to the original type ; but in any 

 case we have these stages between the parasitical breeding- 

 habits of our Cuckoo and the care other species bestow on 

 their eggs and young, and even if there is a wide gap 

 between the lack of the building and incubating instincts, 

 and entrusting the eggs and young entirely to other species, 

 we can find the following intermediate stages to bridge 

 this over. 



First of all we have the fact that, in some species, such as 

 the Pheasant, Partridge, and some of the Cow-birds, two or 

 more females at times lay in the same nest. Further, we 

 find, at times, that odd eggs are deposited by birds in the 

 nests of others of the same or different species, presumably 

 as a result of their own eggs having been taken before 

 laying is completed. For instance, I have seen an egg of 

 the Common Gull in an Oyster-catcher's nest with three 



