326 ON THE EVOLUTION OF PATTERN IN FEATHERS. [Julie 1 8, 



doubtless I have not chosen a correct interpretation of the method 

 employed. The same results can be reached by several ways ; and 

 without a large series of young and immature birds, not only of 

 the particular species but also of those nearly allied, it is impos- 

 sible to form a positive opinion. 



My object has rather been to show that all the many and diverse 

 markings on the feathers of birds are in the main variations of one 

 type, namely : a longitudinal stripe with great tendency towards 

 lateral expansions into transverse stripes, and that on modifications 

 of this, by suppressing one portion or increasing another, all the 

 various patterns have been built up. I have not entered into the 

 question of the more peculiarly marked feathers in the cases 

 where groups of feathers form conspicuous patterns, as such 

 markings must have been subsequently acquired, for the recogni- 

 tion of the species by its own race, and do not in consequence 

 enter into the purport of this paper. The main question that 

 now remains to be answered is that relating to the method in 

 which the pigment groups itself to form these markings, but that 

 is a matter which I hope to be able to investigate when dealing 

 with the question of colour-change. At present I will only say 

 that there is usually, if not always, but one pigment in any 

 particular feather, the difference in shade or colour being due, in 

 the case of shade to a greater or lesser concentration of the 

 pigment, and in the case of colour to surface-structure. 



To sum up — Apart from the main principles of the evolution as 

 shown in the table (p. 318), and through one or other lines of 

 which all birds seem to have passed, it should be noted that the 

 most exposed portions of a bird, generally the upper parts, undergo 

 a further evolution than those less conspicuously situated, and if 

 there be any difference between the sexes, the male shows t he 

 higher form. 



I should like to add that this paper has no pretensions at being 

 in any nay complete or exhaustive. The subject has, so far as I 

 am aware, not hitherto been treated from this standpoint, and I 

 shall be most grateful to any who may care to honour me with 

 their criticisms regarding it. 



EXPLANATION OF THE PLATES. 

 Plate XIX. 

 Figs. 1-13. Diagrammatic representation of the pattern on the feathers of 

 various individuals of the Sparrow-hawk [Accipiter niaus). 

 Fig. 14. Diagrammatic representation of the pattern on the feather from the 

 breast of a Night-Heron (Nyctticorax griseus). 



Plate XX. 

 Fig. 1. Feather from the breast of Wren (Troglodytes parwlus). 



Figs. 2, 3, 4. Feathers from Partridge : figs. 2 & 3 are from young birds. 

 Fig. 5. Feather from Barn-Owl (Strix jlammea). 

 <>. „ „ Scops Owl (Scops giu). 



7. „ „ Golden Plover (Ckaradrius pluvialis). 



8. „ ,, breast of Song-Thrush (Turdus musieui i). 



9. „ „ „ „ Fieldfare (Turdus pilaris). 

 Figs. 10 & 11. „ „ young of Song-Thrush. 



