PRESENCE OF EYES IN SHELLS OF CERTAIN OHITONIDJL 53 
found when the alga was scrubbed off, and at the most recently 
formed margins of the tegmenta not yet encroached upon by 
the plant (PL VI, figs. 10, 11, 12). 
The eyes are very small and their cornese are oval in outline, 
the long axes of the ovals being directed vertically in the direction 
to the heights of the shells. The eye-capsules reach to only a 
small depth in the thickness of the tegmenta. The megalo- 
pores and micropores are disposed in vertical parallel lines with 
great regularity, the megalopores occurring at regular inter- 
vels in the lines of micropores (PI. VI, fig. 11). A consider- 
able proportion of the micrsesthetes are borne on strands inde- 
pendent of the megalaesthetes. The tegmentary surface is 
covered with rows of tubercles, so disposed as to form regular 
series radiating from the apex of each shell, and also corre- 
sponding with one another in position horizontally. The eyes 
are never placed on the tubercles, but lie on the flat surface of 
the tegmentum between them, and it is possibly because of the 
existence of the tubercles all over the tegmentary surface that 
the eyes do not get entirely obliterated in the older regions of 
the shell. 
The eyes are present in enormous numbers. I estimate 
roughly the numbers present on the anterior shell alone at 3000, 
counting only the younger ones, which are in good condition, 
near the free margins of the tegmentum, and not the older 
more or less destroyed by the boring of the shell by algae and 
animals on the rest of the areae. On the remaining shells, at a 
moderate estimate, reckoning as before only the eyes in toler- 
able condition, there must be at least 8500 eyes. 
InEnoplochiton niger the eyes are excessively minute, 
and would not have been recognised at all as such had not the 
larger eyes in other forms been previously studied. They are 
here also confined to the margins of the tegmenta (PI. IV, 
figs. 6, 7, 8, 9). 
The cornea is slightly oval, as in Corephium aculeatum, 
and as in that species the megalopores and micropores are dis- 
posed in vertical lines. 
In Tonicia marmorata the eyes have the peculiarity of 
