Noles and Observations on a Guan. 297 



If, however, we can draw auy conclusions from the very 

 large size of the Guanas egg in relation to the very small 

 size of its actual body when stripped of its feathers^ then we 

 should be tempted to say that this period must have been 

 reduced to very small proportions. 



This disproportion between the size of the bird's naked 

 body and the eg^ is so great that one wonders how a bird 

 of such slim proportions could possibly lay such a large one. 



In other birds, such as the Megapode, it has been recog- 

 nized that disproportion of such a nature has been evolved 

 in order to allow of the whole of the normal period of the 

 nestling stage to be got through within the shell before the 

 young are hatched ; by which it comes about that the young 

 Megapode from the moment of hatching is fully fledged and 

 can fend for itself. 



Taken in conjunction with the remarks made by Sclater 

 and Salvin in reference to the habits of the young of Orialis 

 leucogastra {lac. cit.), the large size of the Guanas egg seems 

 therefore to justify us in concluding that the young Guan 

 at the moment of hatching is in a very advanced condition 

 of development ; and that with such a precocious condition 

 of the inner flight-feathers descent from the tree to tlie 

 ground at a very early stage in its life-history would be 

 rendered comparatively easy. 



The fact of the retarded development of the outer 

 primaries and the statement in regard to the agility dis- 

 played by the chick in clinging to the branches of underwood, 

 is also of great interest, as being reminiscent of ancestral 

 days when it was in all probability entirely arboreal in its 

 habits. 



Geological evidence all points to the fact that the further 

 we go back (within limits) the greater proportion of carbon 

 dioxide there probably was in the atmosphere and the greater 

 the density of vegetation ; and it appears to me that those 

 who might hold that the Guan is only in process of again 

 revei'ting to an arboreal existence could only do so by 

 presuming that at some past geological epoch there must 

 have been a sudden retrograde movement in the amount and 



