]92 Mii'iov 11. F. Meiklejolin oji tie [Ibis, 



Tu any case it lias been impossible to find any abnormality 

 in the struetnre of the Cuckoo to prevent its incubating its 

 eggs. Suggestions to the effect that the hairy caterpillars 

 on which it feeds are so scarce in some seasons that it would 

 not have time to procure food and rear its own young, seem 

 far fetched. 



Lastly, Darwin's statement, which Dr. Rey also mentions, 

 that "the immediate and final cause of the Cuckoo's instinct 

 is that she lays her eggs not daily, but at intervals of two or 

 three days," does not carry conviction with it, but appem's 

 to be confusing cause and effect. 



It seems, however, unlikely that the origin of the p;\rasitic 

 breeding-habits of the Cuckoo will ever be definitely settled, 

 and, having considered the question at some length, we must 

 pass on to study the other peculiarities of tliis species in 

 detail. 



Dr. Reifs Conclusions. 



Having exhausted our facts, the remainder of our know- 

 ledsre rests entirely on theories and conclusions, and these 

 are many and diverse. Among the most important arc the 

 seventeen arrived at by Dr. Eugene Hey*, after many years 

 of careful investigation in Germany, and as these cover most 

 of the main points they deserve detailed consideration. 



They are as follows : — 



(1) The eggs of the Cuckoo (C canorus) vary more in 



colouring and markings than those of any other 

 known species. 



(2) The main distinctive features of the eggs are the greater 



weight of the shell, and especially its thickness and 

 solidity. 



(3) The majority of Cuckoos' eggs resemble, in their 



colouring and markings, the normal tj-^pe of egg of 

 one of the common soft-billed birds. Others are 

 of a "mixed-" type, and many of these do not 

 resemble the eggs of any known species. 



* ' Altesund Neues aus dem Auslialte des Kuckucks,' von Dr. Euo;ene 

 Rey, pp. viii+lOS. Leipzig (Freese), 1892. 8vo. 



