Mutations among Invertebrates 
yellow in wild individuals of either sex and of 
any age. In the blue-fronted Amazon parrot 
(Chrysotts @steva)—a most variable bird—the 
normally red edge of the pinion is sometimes 
yellow. Bateson, in his Materials for the Study 
of Variatzon, gives other examples of this kind 
of variation. 
As further instances of mutations among 
animals which have been observed in nature, we 
may mention the valezina form of the female of 
the Silver-washed Fritillary Butterfly (4zzynnzs 
paphia) and the helice form of the female Clouded- 
yellow Butterfly (Colas edusa). 
The common jelly-fish is an organism which 
frequently throws off sports, and some zoologists 
are of opinion that the medusoid Pseudoclytia 
pentata arose by a discontinuous variation from 
LEpentheses folleata or a closely allied form. 
Thomson discusses this particular case at some 
length on pages 87-89 of his Heredity, and gives 
it as his opinion that the evidence in favour 
of this latter having arisen as a mutation is 
“exceedingly strong.” 
It is our belief that many species of birds 
which occur in nature have been derived from 
other species which still exist, but as no one has 
ever seen the mutation take place, we cannot 
furnish any proof thereof. We merely rely on 
the fact that the species in question differ so 
slightly from one another that there seems every 
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