56 BULLETIN OF THE 
Graber (’79, pp. 84, 85, Figg. 13, 14) found that in the median eyes 
of Buthus there was left, after the action of caustic potash had made 
the central portions of the sections paler, a rose-colored granular rim or 
marginal zone, and that in this zone were to be seen a few, mostly in- 
distinct, nuclei and markings perpendicular to the sclera, which together 
might serve at first sight to suggest the presence of a tall cylindrical 
epithelial sclera-matrix. This view Graber definitely puts aside, how- 
ever, and concludes that the appearance is due to the oblique direction 
of the section, the apparent epithelium being only the cut-off (anterior) 
ends of “ Retinaschliéuche.” But inasmuch as there are no other sub- 
cuticular (subscleral) structures, these “ retinal sacs” have assumed, in 
his opinion, notwithstanding their other functions, the réle of matrix- 
cells. 
Even without our present knowledge of the manner in which similar 
eyes arise, this interpretation would be unsatisfactory, because the mar- 
ginal zone is most sharply marked off from the retina in the posterior half 
of the ball of the eye, and it would be difficult to imagine the course of 
retinal cells which in this region could be so cut as to give rise to the 
appearance figured. But I do not doubt the accuracy of the figure in 
question (Graber’s Fig. 14), and believe that its interpretation becomes 
easy when considered in connection with the probable origin of the re- 
tina. If the median eye in Buthus was formed by an involution with 
inversion of the retina, Graber’s “ Matrixzone”’ would be the posterior 
layer of that infolding, and its gradually merging into the retinal layer 
in the anterior half of the ball of the eye would be entirely parallel to 
what occurs in the formation of the “ pre-nuclear ” eyes in spiders. 
Lankester and Bourne (’83) have also had under consideration this 
pigment- and matrix-zone of Graber, and have arrived at conclusions 
which are entirely new. It will be most satisfactory to quote their own 
words upon what they call “intrusive pigmentary connective tissue :” 
“The structures which we consider as intrusive connective tissue in the 
central eyes of the Scorpion may be compared to the interneural cells 
of the lateral eyes. Like these, they are pigmentiferous, and serve 
to fill up the spaces between the several nerve-end cells and between 
these and the ommateal capsule. But whilst we regard the interneural 
cells as ectodermal in origin, . . . we find reasons for considering the 
intracapsular pigmentary connective tissue of the central eyes of Scor- 
pions as derived from mesoblast, and of the nature of connective tissue. 
“We have not embryological evidence for this conclusion, and depend 
entirely upon the branching, inosculating character of the pigmentary 
