PLATE 1 
EXPLANATION OF FIGURES 
1 Outline drawing of Ornithorhynchus anatinus, to show the location of the 
various hair tracts. A, modified shield hair of the chin; B, fur hair of the ear; 
C, area of pigmented, truncated shield hair; D, area of unpigmented, truncated 
shield hair; Z, truncated shield hairs of feet and venter of tail; ”, shield hair of 
dorsum; G, large shield hair of dorsum of tail. The areas F and G lack the fur 
hair. None of the areas are sharply defined (with the exception of the area of the 
ear), but merge gradually into one another. X }. 
2 Arrangement of the folliclesof the shield hair and fur hair on the dorsum 
(after Meijere). A, shield hair; B, bundles of fur hair. X 200. 
3 to 11 illustrate the various typesof hairfound on Ornithorhynchus (cir. nat. 
size). 
3 Shield hair from the dorsum. 
4 Shield hair from midway between the eyes. 
5 Shield hair from the proximal end of the tail. 
6 Shield hair from the distal end of the tail. 
7 Shield hair from the venter. 
8 Modified shield hair from the chin. 
9 Fur hair of the dorsum and venter. 
10 Fur hair from the area of the ear. 
11 Shield hair from the area of the ear. 
12 Guide figure. 
13 Shield hair at point 0, figure 12, showing the cuticular scales. M, medulla; 
CO, cortex. X 800. 
14 Shield hair at m—n, figure 12. B, shaft; C, isthmus; D, shield; MV, medulla; 
CO, cortex. X.800. 
15 Shaft of shield hair at p, figure 12. M, medulla; CO, cortex. X 800. 
16 Shaft of shield hair below gq, figure 12. B, bulb; M, medulla; CO, cortex. 
« 800. 
17. Shield of shield hair. MM, medulla;CO, cortex; CU, cuticle; M’, vestiges of 
the medulla which often persist near the base of the shield. > 400. 
18 Guide figure. 
19 Transverse section through various portions of the shield as shown by 
the guide figure, figure 18. Letters indicate where the sections were made. Note 
the greater thickness of the cuticle on the ectal surface of the shield. x 90. 
20 Transverse sections through the shaft of the shield hair, midway from the 
base of the shaft to the isthmus. M, medulla; CU, cuticle; CO, cortex. X 280. 
21 Transverse section through the shaft of the shield hair near the base of 
the shaft just above the mouth of the follicle. M, medulla; CU, cuticle; CO, 
cortex. XX 280. 
22 Shaft of the shield hair, dissected. CU, cuticle, intact; CO, long distorted 
cells of the cortex exposed, after the removal of the cuticular scales; M, medullary 
cells exposed after the removal of the cortex element. X 2400. 
488 
