564 BALDWIN SPENCER AND GEORGINA SWEET. 



open tube. At a higher level, that is right in the epidermis, there 

 is a more clearly outlined tubular space ; but here, in the part 

 immediately above the developing hair, there is merely a more 

 or less loose corneous network up through which the hair 

 pushes its way. This feature in the development of the hair 

 is true of both Echidna and Ornithorhynchus, and can be 

 seen in sections taken from any part of the body. We have 

 seen it in sections taken from the following parts : the top of 

 the head, the shoulder, the middle of the back, the thigh, 

 under the tail, the chin. It is quite true that in the epidermis 

 itself, and leading down into the very uppermost part of the 

 follicle, there is a tubular space present, but this is only 

 formed when, and not until, the hair has developed to a very 

 considerable extent, usually for about three quarters of the 

 length of the follicle; until it reaches the level of the very top 

 of the follicle the hair simply, as described, pushes its way 

 up through the corneous network which forms the inner root- 

 sheath, and only reaches the more open tubular part when its 

 tip lies a short way beneath the surface. 



Stage 7 (fig. 21). — In this stage the hair itself can be 

 readily distinguished, with the pigment extending in an 

 unbroken way almost to the very tip. There is no distinction 

 to be drawn between medulla and cortical substance; the 

 cuticle towards the tip has the characteristic serrate outline. 

 The inner root-sheath in the lower part of the follicle through 

 which the hair has passed has become more compact, owing 

 doubtless in part to the pressure of the hair, while just 

 around and above the tip of the hair the network is clearly 

 seen, and here it takes the stain more deeply than elsewhere. 

 In the somewhat swollen part near to the vipper end of the 

 follicle the network is very clearly seen ; and within the 

 incompletely formed cavity is a certain amount of granular 

 material, produced apparently by the breaking down of certain 

 of the cells. Above this the tubular lumen, now for the first 

 time freely open, leads to the surface. In the lower part of 

 the follicle and in the bulb region we begin to see a more 

 clearly marked diflFerentiation of layers than in the last stage. 



