192 EDWARD B. POULTON. 
the rods in Fig. 1 is partly a longitudinal section of the tube and partly that 
of the papillary processes (as seen in transverse section in Fig. 3). The 
lower end of the complete rod is seen to rest on three touch-bodies, of which 
two are in longitudinal and one in transverse section. Medullated nerve- 
fibres approach the touch-bodies, and a fibre is shown entering the base of one 
of them. 
Fic. 2.— x rather over 400 diameters. Vertical section through the 
upper part of a push-rod and the adjacent corneous epidermis of the bill. 
From the same locality as Fig. 1. The thin flattened cell-plates form nearly 
hemispherical shells which, placed one over the other, build up this part of 
the structure. The form and arrangement suggest a structure which would 
easily yield to pressure, but would be instantly restored to the former level on 
its withdrawal. 
Fic. 3.— x rather over 400 diameters. Horizontal section of the epidermis 
of the bill (locality unnoted, but appearance typical) taken rather below the 
corneal layer. The push-rod in transverse section is clearly seen to consist 
of the following layers, the epithelial cells being represented by their nuclei. 
(1) Centrally, the axial group of filaments: these are very highly refringent, 
and stain with great difficulty; they are probably partially or completely 
corneous. (2) A single layer of deeply staining epithelial cells. (3) The 
circle of filaments, similar to those of the axial group; they are arranged with 
great regularity. (4) A single layer of rather deeply staining epithelial cells. 
(5) A single layer of very faintly staining epithelial cells. (6) The outermost 
epithelial circle, seen by comparison with Fig. 4, to consist of several layers 
of cells which stain deeply. Outside this are the deeply staining fusiform cells 
of the general epidermis. Three papillary outgrowths are seen in section. 
I'ie. 4.— x over 600 diameters. Longitudinal section of a push-rod, with 
the transverse section diagrammatically rendered. From nearly the same 
locality as Fig. 1, but, in this case, from the very margin of the bill. The 
layers described in the last figure are here indicated by the corresponding 
numbers. The appearance represents the details as they can be made out 
with high powers and the most favorable sections. The filaments are seen 
to have a ladder-like appearance, apparently due to their constitution out of 
short sections, the length of which corresponds to the thickness of the cells 
of layer 2. The appearance suggests that each section may be contributed 
by the inner end of the adjacent cell. The same is true of the filaments of 
the circle (3) as regards the cells of layer 4, although in some cases the 
sections appeared rather to correspond with the outer ends of the cells of 
layer 2. The correspondence between the sections and adjacent cells is not 
well represented in the figure. The flattened imbricated cells of layers 2 and 
4 are seen to be swollen at the spot where the nucleus is situated, where 
also there is a special accumulation of pigment. In transverse section of the 
rod, the cells of all the layers have the form of flattened curved plates, and 
