OF THE PARTS OF FEATHERS. 7 



of the bird, has a farrow throughout its whole length ; this is more or less obliterated below 

 towards the tube, where it terminates in an umbiliciform pit, which leads into the interior of the 

 tube. But in the fresh feather a small process of the series of cells occupying the tube projects 

 from this pit (fig. 18, a), and thus closes the opening which penetrates into the interior of the 



the entire barb forms a narrow band-like strip, which is at first distinctly, but afterwards only 

 imperfectly separated from its neighbours, and finally loses itself in a perfectly homogeneous and 

 uniformly granular mass. We will now trace a single strip upwards, from the point at which it is clearly 

 recognisable as such, to its full evolution into a perfect barb. 



In figure 14 I have shown the inferior extremity of one of these strips under the same magnifying 

 power of 500 diameters. The figure shows distinctly enough that it consists entirely of equal-sized, 

 loosely united cells, the perfectly similar elliptical nuclei of which show no trace of a nuclear corpuscle, 

 a circumstance which has led me to suppose that these nuclear corpuscles are only formed at a later 

 period, and are probably to be regarded as cavities of the nucleus. At this inferior extremity the 

 strip appears to be perfectly flat, but higher up it becomes curved, and still higher triangularly 

 prismatic. In this form one sharp edge of the prism is directed outwards towards the follicle, and by 

 the two others each prism is applied to its two neighbours. The flatter side, which in this position is 

 turned towards the matrix, is not really flat, but somewhat hollowed, and into this cavity a membranous 

 fold penetrates, which at the first glance appears to be a fold of the matrix itself, but is really derived 

 from a peculiar membrane situated between the matrix and the feather-material. In some cases I have 

 seen blood-vessels in this membrane ; in others I have distinctly recognised cellular structure, and 

 indeed cells similar in formation to those seen in the strip. The latter condition belongs probably 

 to an early, and the vascular condition to a later period of the membrane. As soon as the for- 

 mation of the barb is completed, however, it separates from the membrane, and the latter remains, in 

 the form of a perfectly close dry sac, with its surface finely lined, in the cylinder of the feather above 

 the matrix. From, it originate the dry membranous structures, which are perceptible above the upper 

 extremity of the matrix (Plate I, fig. 11, dtl), and which project from the umbiliciform pit at the 

 upper end of the tube (fig. 18, a). These parts acquire the aspect of cells, or rather saccules, appa- 

 rently in the following manner : as soon as they begin to become dry above, the matrix forms a new 

 layer beneath the old ones, and pushes this into the others. These membranes are therefore never 

 true closed sacs, but merely caplike pouches, partly stuck one into the other like conical sugar-papers. 

 The "soul" (Seele) or pith in the interior of the tube (fig. 18, c) is formed in the same manner, from 

 which it follows that this also is to be regarded as the partially thrown-off outer layer of the matrix. 

 The reason why no striation is observed on the surface of these pouches of the pith is perfectly 

 clear, the cylinder of the tube being smooth, and not striated. We must now return to the examination 

 of the barb. 



If the prismatic strip be spread out upon a flat surface, at a point where it already possesses the 

 above-mentioned oblique lines on each side, we obtain the appearance shown in fig. 15. I must, 

 however, remark, that the preceding figure (14) was taken from the colourless feather of a goose, and 

 this from a gray pigeon's feather. In the colourless barb of a feather neither the dark spots in the 

 middle of the future central stem, nor the sharply circumscribed dark spots upon the barbules are to 

 be seen ; both are unquestionably accumulations of pigment, and in those of the central part I could 

 very distinctly recognise the branch-like excrescences emitted by every pigment-cell, which, moreover, is 

 much larger than one of the primitive cells. If the feather be colourless the oblique striaj on each side 

 of the barb are much less distinctly seen, but at the same time it shows all the more clearly that each 

 stria is produced by the separation of a series of cells running obliquely across the lateral surfaces 

 of the prism, and that this separation becomes more and more complete, the nearer the position of the 



