circumference is nearly 1.5 mm. The greater thickness of [98] 

 the skin on the ventral side at the base is due principally 

 to the epidermis, the corium being more nearly uniform 

 throughout. In the thickened area the epidermal ridges ex- 

 tend down deep into the cutis, and the papillae are very long 

 and slender. The various integumentary organs, sweat glands, 

 sebaceous glands and hairs, are numerous and of normal 

 build. In longitudinal sections (Fig. 4) it may be very plainly 

 seen that the hair follicles are obliquely inserted, the hair 

 pointing towards the tip of the appendage. This is with- 

 out exception the case in the proximal two-thirds of the tail, 

 although the regular arrangement is somewhat disturbed at 

 the crease where the distal and middle segments join, especi- 

 ally on the left side. The corium contains a very abundant 

 supply of elastic fibres which may be readily demonstrated in 

 sections stained by Weigert's method. 



Beneath the skin the main bulk of the tail is made up of 

 areolar tissue containing much fat. Blood-vessels, nerves, 

 and striated muscle fibres are imbedded in this mass. There 

 is no trace of anything like the medullary cord or of noto- 

 chordal tissue, as Gerlach found in the tail of a foetus of four 

 months. 



The voluntary muscle consists of a few bundles of fibres 

 which take origin from the subcutaneous areolar tissue near 

 the proximal end of the middle segment. They lie on the 

 left side not far from the mid-line (Figs. 4 and 5), and run 

 distally in parallel bundles diverging somewhat towards 

 their insertion in the skin just beyond the joint- between the . 

 middle and distal segments. The majority of the fibres are 

 attached on the left side; a few, however, pass to the skin of 

 the right side; and others are attached to the dorsal surface, 

 and perhaps a few ventrally. The action of the muscle is 

 thus clearly explained by its anatomical relations. There 

 are no muscle fibres running between the trunk and the tail. 



On the right side near the middle of the tail there are a 

 few muscle fibres (Fig. 5, M'), but these are isolated in small 

 bundles or as single fibres by a dense stroma of connective 

 tissue. Moreover, nearly all of these fibres are in a state of 



(7) 



