Mutations among Invertebrates 



yellow in wild individuals of either sex and of 

 any age. In the blue-fronted Amazon parrot 

 (Chrysotis cestiva) a most variable bird the 

 normally red edge of the pinion is sometimes 

 yellow. Bateson, in his Materials for the Study 

 of Variation, 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 (Argynnis 

 paphia) and the helice form of the female Clouded- 

 yellow Butterfly (Colzas 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 

 Epenthesis 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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