112 S. HIROTA. 



masses and some branched pigment cells) which is a direct continuation 

 of the pia mater. In cases where the regenerated spiiial cord is absent, 

 this connective tissue alone seems to fill up the canal of the cartilaginous 

 axial skeleton. 



To return to the transition point of the vertebral column into the 

 cartilaginous cylinder, the last vertebra left is not entire but is repre- 

 sented only by its anterior half, what is exactly to be expected, if the 

 fracture occurred at the usual position, that is to say, at the vertebral 

 body and not intervertebrally. Sections of the half vertebra just men- 

 tioned, to be met with for a short distance behind the plane (6) of fig. '2, 

 certainly present the same or similar appearance as that shown in fig. 5. 

 At its posterior end, the half vertebra, or rather its marrow-mass, 

 j)asses directly and so far as could be ascertained from cross-sections 

 abruptly, into the cartilaginous cylinder without an appreciable change 

 either in thickness or in calibre of the vertebral canal. This transition, 

 indicating the position where the tail was torn off, takes place in perfect 

 harmony with what I have speculated from the condition of external 

 scales ; viz., at about the plane of the hind edge of the second whorl of 

 scales behind the crotch. 



There can be no doubt whatever as to the nature which I have 

 assigned to the half vertebra. Its size, shape and structure forbid us to 

 entertain the idea that it is a new vertebra in process of being formed 

 at the anterior end of the cartilaginous tube. 



With respect to the internal structure of the accessory tail (ligs. 

 4-7), let it at once be stated that only the peripheral organs of the main 

 tail are involved in its constitution. Beneath the integument and the 

 subdermal connective tissue layer, there is a layer of well-developed 

 muscles enclosing axially a space filled with an areolar cuimective tissue, 

 in which are scattered ramified pigment cells (fig. \()). All the parts 

 just mentioned are continuations of corresponding parts in the main tail. 

 The accessory tail is innervated by two comparatively thick nerves of 

 quite ordinary structure. The left end of fig. 4 {section at the plane 

 of (4) in fig. 2) brings to view the two nerves just entering it. I have 



