600 THE DESCENT OF MAN 



and of an Indian pigeon {Ghalcophaps indicus), are trans- 

 versely 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 

 (Ohrysococcyx), the mature species differ considerably 

 from one another in color, but the young cannot be dis- 

 tinguished. The young of an Indian goose {Sarkidiornis 

 melanonotus) closely resemble in plumage an allied genus, 

 Dendrocygna, when mature.' 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 cer- 

 tain other species, for instance, the red grouse or T. scoiicus. 

 Finally, as Mr. Blyth, who has attended closely to this sub- 

 ject, 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 confirms 

 the belief that the immature plumage approximately shows 

 us the former or ancestral condition of the species. 



Although many young birds, belonging 'to various fami- 

 lies, thus give us a glimpse of the plumage of their remote 

 progenitors, yet there are many other birds, both dull col- 

 ored and bright colored, in which the young closely resem- 

 ble 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 plu- 

 mage of their progenitors, excepting in so far that, when 

 the young and the old are colored in the same general 

 manner throughout a whole group of species, it is prob- 

 able that their progenitors were similarly colored. 



' In regard to thrushes, shrikes, and woodpeckers, see Mr. Blyth, in 

 Charlesworth's "Mag. of Nat. Hist.," vol. i., 1837, p. 304; also footnote to 

 his translation of Ouvier's "R^gne Animal," p. 159. I give the case of Loxia 

 on Mr. Blyth's information. On thrushes, see, also, Audubon, "Omith. Biog- 

 raphy," vol. ii. p. 195. On Chrysocoocyx and Chalcophaps, Blyth, as quoted 

 in Jerdon's "Birds of India," vol. iii. p. 485. On Sarkidiornis. Blyth, in 

 "Ibis," 1867, p. 175. 



