3hap. XVI. Birds — Inheritance Limited by Age. 465 



The young of many species of shrikes (Lanius), of some wood- 

 peckers, and of an Indian pigeon {Chalco^ltaps indicus), are 

 transversely striped on the under surface; and certain allied 

 species or whole genera are similarly marked when adult. In 

 some closely-allied and resplendent Indian cuckoos (Chryso- 

 coccyx), the mature species differ considerably from one anothe? 

 in colour, but the young cannot be distinguished. The young 

 of an Indian goose (Sarkidiornis melanonotus) closely resemble 

 in plumage an allied genus, Dendrocygna, when mature. 1 

 Similar facts will hereafter be given in regard to certain herons. 

 Young black grouse (Tetrao tetrix) resemble the young as well 

 as the old of certain other species, for instance the red grouse 

 or T. scoticus. Finally, as Mr. Blyth, who has attended closely 

 to this subject, has well remarked, the natural affinities of 

 many species are best exhibited in their immature plumage; 

 and as the true affinities of all organic beings depend on their 

 descent from a common progenitor, this remark strongly con- 

 firms the belief that the immature plumage approximately 

 shews us the former or ancestral condition of the species. 



Although many young birds, belonging to various families, 

 thus give us a glimpse of the plumage of their remote pro- 

 genitors, yet there are many other birds, both dull-coloured and 

 bright-coloured, in which the young closely resemble their 

 parents. In such cases the young of the different species cannot 

 resemble each other more closely than do the parents ; nor can 

 they strikingly resemble allied forms when adult. They give us 

 but little insight into the plumage of their progenitors, excepting 

 in so far that, when the young and the old are coloured in the 

 same general manner throughout a whole group of species, it is 

 probable that their progenitors were similarly coloured. 



We may now consider the classes of cases, under which the 

 differences and resemblances between the plumage of the young 

 and the old, in both sexes or in one sex alone, may be grouped. 

 Rules of this kind were first enounced by Cuvier ; but with the 

 progress of knowledge they require some modification and am- 

 plification. This I have attempted to do, as far as the extreme 

 complexity of the subject permits, from information derived 

 from various sources ; but a full essay on this subject by some 

 competent ornithologist is much needed. In order to ascertain 



1 In regard to thrushes, shrikes, On thrushes, see also Audubon, 



and woodpeckers, see Mr. Blyth, in 'Ornich. Biography,' vol. ii. p. 195 



Charlesworth's ' Mag. of Nat. Hist.' On Chrysococcyx and Chalcophaps, 



vol. i. 1837, p. 304 ; also footnote Blyth, as quoted in Jerdon's ' Birds 



to his translation of Cuvier's ' Rrgne of India,' vol. iii. p. 485. On Sar- 



Animal,' p. 159. I give the case kidiornis, Blyth, in ' Ibis,' 18b7, p 



of Loxia on Mr Blvth's information. 175. 



2l" 



