EK. W. BERGER ON THE CUBOMEDUSA. 43 
of it remains. As concerns most of my series I could not well 
determine which were from younger and which from _ older 
individuals, yet, several series of quite small (6mm.) and therefore 
young animals, in which the eyes were so small that the lenses were 
compassed into less than half a dozen sections, the cellular structure 
of the lens was very evident. 
The external cells of the lens form a spherical shell (both complex 
eyes) which, in section, shows as a hollow ring (Figs. 7, 13). The 
thicker ends of these cells lhe at the inner (toward the capsule) half 
of the sphere and the cells taper toward the corneal surface, dove- 
tailing laterally with their immediate neighbors as also distally with 
those from the opposite side of the sphere. The thicker inner ends 
of the cells contain the large nuclei with nucleoli. At a point (*Figs. 7 
and 13) on the inner (next the capsule) surface of the lens the cells only 
approximate each other and thus leave a place which is easily 
broken through, as is shown by portions (drops, probably representing 
cells or portions of cells) of the mass within the lens becoming 
squeezed out into the substance of the capsule and the vitreous body, 
and found occasionally also among the cells of the retina. A 
considerable portion of the inside of the lens may be found thus 
squeezed out, and its path can often be traced. This phenomenon is 
evidently brought about by a contraction of the shell of the lens 
during fixation and before the inside of the lens has become 
hardened. 
In origin the lens is evidently ectodermal, originating from an 
ectodermal invagination which becomes pinched off as a hollow 
sphere, the outer (2. e. next the cornea) half of which becomes the 
lens, the inner half the retina (¢. e. vitreous body plus the so called 
retina). (See Retina.) The transition from retinal to lens cells is 
quite readily made out at the lower side of Fig. 7, but the corres- 
ponding structure on the upper left side is not so manifest. It is 
further evident that the lens is again an invagination into this 
sphere, and the point at which the lens cells approximate (where the 
central mass of the lens may be squeezed out as above described) 
represents the place of pinching off of the original lens-retina sphere. 
It appears, then, that the lens is formed in the lens-retina sphere in 
the following manner: The cells of the secondary invagination 
going to form the lens begin to lengthen distally (7. e. toward the 
cornea) during their invagination to form a hollow sphere, at the 
