A Tlicorij of the Parasitic Rah it of the Cachjo. G7 



Since coming to the above conclusions, I liave luul the 

 pleasure of reading Prof. G. II. T. Einier's recently published 

 work on the " Origin of Species." According to Eimer 

 variations are few in number, definite in character, and 

 determined by the conditions of growth. This is a consti- 

 tutional theory of evolution. I was much pleased to find 

 as a minor point in tliis interesting and important work, 

 a discussion of the cuckoo's instinct, which, in the main, 

 harmonises with that whicli I have just sketched. The 

 subject is both beautifully and fully dealt with, and I shall 

 therefore conclude by summarising Elmer's position. 



He briefly criticises the Darwinian explanation, which 

 appears to him to involve too many happy combinations. 

 He believes that what is inherited in the establishment of 

 the habit, is not the device itself, which one can hardly 

 believe, but the influence of the foster upbringing. He 

 maintains, and I of course agree, that the ancestral cuckoo 

 acted deliberately in the trick, and some of this deliberateness 

 of device may still persist. The explanation of the unnatural 

 habit he finds in the bird's whole character and mode of life. 

 In this connection he emphasises {a) the vagabond, restless 

 habit ; (h) the looseness of the sex relations, strong in passion, 

 weak in love ; (c) the irregular and gluttonous nutrition con- 

 sidered in relation to reproductive stimulus ; {d) the slow 

 laying of the eggs, itself dependent upon nutrition, and 

 pointing to physiological conditions which modify even the 

 deeply rooted impulse and instinct to brood ; (e) the 

 degeneration of social instincts and the preponderance of 

 egoism. The essential similarity of Elmer's views with mine, 

 is interesting to myself, and possibly corroboratory to others. 



Works referred to. 

 Brehm's Thierleben. 

 Darwin's Origin of Species. 

 Eimer's Die Enstehung der Arten auf Grund von Yerer- 



ben erworbener Eigenschaften nach den Gesetzen 



organischen AVachsens, Jena, 1888. 

 EoMANES, G. J., Animal Intelligence, Int. Sci. Ser., London, 



1886. 



