220 Dr. W. B. Carpenter on the Structure [Jan. 20, 



wards through the middle of the quinquelocular dilatation of its cortical 

 cylinder (as shown at g, h, fig. 3), just as in a flower the axis which 

 forms the style of a multilocular ovary passes upwards through the 

 midst of the carpels which are clustered around it. In the upward 

 course of this " axial prolongation," as it may be provisionally termed, 

 it first passes through the central aperture of the " rosette," and then 

 through the vertical canal which is left by the truncation of the wedge- 

 like First Radials, thus reaching the base of the cavity of the calyx, and 

 constituting the " pedicle," of which I have already spoken, as the chief 

 attachment existing between the basal (or dorsal) surface of the lenticular 

 visceral mass and the concavity of the calyx. This "pedicle" (h, fig. 2) 

 enters the " axial canal " (g) previously described as passing upwards 

 towards the oral pole, and may be traced along its whole length (gene- 

 rally more or less imbedded in its wall) to the point at which that canal 

 subdivides into the five subtentacular canals which underlie the radial 

 furrows of the disk. Here the axial cord appears to spread out into a 

 plexus which surrounds the mouth ; and this plexus is continued towards 

 the periphery of the disk underneath the radial and brachial canals, every 

 one of which usually has a cord running along each of its margins, con- 

 nected by transverse branches with the cord of the opposite side. At 

 or near the margin of the disk the two cords of each brachial canal seem 

 to coalesce into a single one ; and this runs onwards between the subten- 

 tacular and the cceliac canal of the arm (as shown at gr, fig. 6), 

 giving off branches which pass into the sexual pinnules; and these 

 branches are continuous with the testes or ovaries which these pinnules 

 contain. 



Hence it would appear' that this " axial cord " is (in part, at least) 

 a generative rachis, furnishing the germs which are to be developed into 

 the proper sexual products ; and this view I find to be confirmed by 

 minute examination of its structure. At the point at which it dilates 

 into the cavity of the ovary, it is clearly a tube containing minute cor- 

 puscles of about l-3000th of an inch in diameter; and from these corpuscles 

 to complete ova every stage can be traced. Following the cord back- 

 wards towards the plexus of the disk, I find it still to possess the same 

 tubular wall and granular contents ; in the plexus itself the cavity with 

 its granular contents bears a smaller proportion to the thickness of the 

 tubular wall ; but the " axial prolongation," from which I believe this 

 plexus to arise, often seems at the period of generative activity to be 

 almost made up of such corpuscles. 



I confess that I have not yet been able to trace the absolute continuity 

 of the generative plexus of the disk with the axial cord of the adult 

 Antedon, the dissection of the parts around the mouth being made very 

 difficult by the quantity of loose connective tissue which forms the 

 annular lip. The termination of the axial prolongation and the origin of 

 the plexus in the same locality obviously point to such continuity ; but 



