EXTERNAL PABTS OF BIRDS. —FEATHEBS. 



83 



the casts of the lateral furrows, as well as hotweeu each of the minor grooves, and the hollow 

 cone would expand into a flat feather-like structure with a median shaft, as a 'vane' formed 

 of ' barbs ' and ' barbules.' In point of fact, in the development of a feather such a cast of the 

 dermal papilla is formed, though not in gelatine, but in the horny epidermic layer developed 

 upon the mould, and, as this is thrust outward, it opens out in the manner just described. 

 After a certain period of growth the papilla of the feather ceases to be grooved, and a continu- 

 ous homy cylinder is fonned, which constitutes the ' quill.'" (Introd. Classif. Anim., p. 71.) 





Fig. 18. —Symmetrical FigiireR from Forming Feathers; tt, dove; h, turkey. — " In tbe summer of 

 1869, whilst examining the feather capsule of a nestling dove, tbe microscopic slide was suddenly covered with a 

 multitude of exquisite forms . . . The next day my German farmer climbed to the dove's nest and procured a few 

 more pin-feathers. Some of these were cut into tine shreds, rubbed in a drop of water, and placed under the 

 microscope. In a short j)eriod the figures of yesterday were again before me. From the cut Burfaces of the 

 portions of the pin-feathers I had placed under the lens, granules appeared to stream forth like blood, covering 

 the microscopic slide in countless numbers. Mingled with these were numerous larger cells of a globular or oval 

 form, having a transparent centre. The^o and the granules gave to the water a slightly glutinous consistency. 

 As the fluids on the glass dried, lines at different angles shot across the slide, looking mucli as though an 

 unseen camel's hair pencil had been swiftly drawn in opposite directions, sometimes at right angles, but frequently 

 at angles more acute. Probably at the moment uf transition from a fluid to a solid condition, the transparent 

 nucleated cells assumed the form of a square, a lozenge, a starry hexagon, a cross, or any other beautiful figure 

 which could be formed of the parts which suddenly appeared in the spherical cells, these parts seeming at first, in 

 some instances at least, to consist of minute triangles. At the same moment the little granules moved to order, 

 and there before the astonished gaze were diamonds such as Aladdin might have envied, in form as varied, but far 

 more symmetrical, than the frost-work on a window pane of a winter's morning." (I\Iiss Grace Anna Lewis, in 

 Am. Nat., v, 1871, p. 675.) 



