The Making of Species 
and the golden form of the common carp among 
captive animals; and among animals in a state 
of nature, yellow forms have been recorded of the 
rose-ringed Paroquet (Paleornis torguatus), the 
green woodpecker, the pike, and the eel. These 
lutinistic forms usually have normally coloured 
eyes. Sometimes, but only very rarely, these 
yellow forms throw off white sports—as, for 
example, the “silver” form of the goldfish. 
Finn has seen a white variety of the common 
carp. White canaries are excessively rare, while 
white budgerigars are unknown. 
It is worthy of note that entirely yellow species 
of birds and fish are unknown. We would suggest 
that the explanation of this is that yellowness is 
correlated with some physical characteristic un- 
favourable to an organism exposed to the 
struggle for existence; hence individuals which 
are yellow are not permitted to survive. In some 
species of moths individuals occur in which the 
parts normally red are yellow. According to 
Bateson, a chalk pit at Madingly, near Cam- 
bridge, has long been known to collectors as a 
habitat of a yellow-marked form of the six-spot 
Burnet Moth (Zygena filipendule). These 
lutinistic forms are not confined to one genus 
of Butterflies. Moreover, in the Pin-tailed Non- 
pareil Finch (Zythrura prasina) of the Eastern 
Archipelago the red tail and other red parts of 
the plumage are not infrequently replaced by 
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