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PINEAL EYE OF YOUNG AND ADULT AWNGUIS FRAGILIS. 91 
round, and therefore of embryonic character. Perhaps 
the reason is that I examined the smallest of the adult 
blindworms which I possessed. It measured only 23 cm., 
whereas the mother of the young blindworms was 35 
em.in length. If I had examined such a large and quite 
mature specimen, possibly all the cells of the lens would 
have been found to be fusiform. 
I have mentioned already, that in the young Angwis the 
lens lies close on the pigment layer of the retina, or in 
other words, that the cavity of the vesicle, as it is com- 
monly called, has not yet made its appearance. ‘This 
arrangement furnishes an argument against the usual 
opinion in regard to the formation of the vesicle of the 
pineal eye. Spencer supposes that the epiphysis and its 
eye is an outgrowth from the central nervous system, 
and that the cavity of the vesicle is derived from that of 
_ the neural canal. There can be no doubt about the first 
point, and there is also ample proof that the cavities of 
the epiphysis proper are derived from the neural canal, 
but my preparations of the young Anguwis show, that the 
theory does not hold good for the cavity of the vesicle. I 
am of opinion that that cavity is formed by splitting, 
perhaps by the operation of a fluid which is secreted by 
the surrounding tissue pushing apart the two layers of 
cells. This fluid, lying between lens and retina, would then 
be analogous to the vitreous humour of the paired eye. 
In the tissue separating the pineal eye from the outer 
world, and placed between a layer of connective tissue and 
the epidermis, there is a molecular mass apparently of 
semi-fluid nature, with very few cells scattered init. Some 
of those cells are elongated and pointed, and have quite 
the appearance of sensory cells. This structure is not 
present in the adult, and I have no satisfactory explanation 
of it to offer. Perhaps we might say, that the structure is 
