tourlS/TpTuTrST ^^^^^ Microscopical Society. 209 
II. — On the Fibres of the Crystalline Lens of Petroniyzonini. 
With a Note on the Esophagus of the Aye-Aye. 
By Geobge Gulliver, F.K.S. 
(Communicated by W. H. Ince, F.E.M.S., F.L.S.) 
(Bead before the Royal Mickoscopical Society, March 10, 1869.) 
An extensive comparative survey of tlie fibres of the crystalline lens 
of vertebrate animals would be likely to afford some interesting and 
valuable results for zoology and physiology. 
I know of no recent observations on the subject. Since the 
discovery by Brewster of the junction of the edges of these fibres 
by sinuous or dentated suture, the excellent examples which that 
philosopher gave of it in fishes were truly accepted as conclusive, 
so far as it had been examined. 
But there are fishes in which the fibres of the lens differ re- 
markably from those just mentioned as well known in this class, 
and of which difference a curious illustration is now to be given. 
Of the Lamprey (Petromyzon fluviatilis), the fibres of the 
crystalline lens when highly magnified (Fig. 1, p. 211) appear long, 
flexible, quite smooth, of nearly equal breadth in a great part of 
their length, and commonly flattened ; and being joined together 
laterally by level and straight sutures, the fibres are very easily 
separable from each other. Though colourless and transparent, 
they refract the light so as to present their otithnes distinctly ; and 
when spread out in a sufficiently thin layer, recall to mind certain 
forms of tendinous and elastic tissues ; but the lens-fibres neither 
branch nor anastomose. 
As a mere microscopic object the lens of the Lamprey is 
interesting. The whole of it may be easily teazed out into a con- 
geries of fibres, when its transparency is as completely destroyed as 
that of glass by pulverization. Thus to the naked eye the parts of 
the lens torn asunder appear white and opaque ; but, when further 
separated by the aid of needles and viewed by transmitted light 
under an achromatic object-glass of one-tenth of an inch focal 
length, the fibres are beautifully hyaline and distinct, many wavy 
and curled, some nearly or quite straight and parallel, and others 
sweeping in bold smooth curves among the rest (Fig. 1, showing 
fibres of the prevailing size). Under a lower magnifying power, 
the aggregated and separated fibres remind one of locks of human 
hair thrown carelessly on a flat surface. 
" In fishes," says Johannes Miiller, " the internal laminaa of 
the lens have an extraordinary hardness, almost like that of horn." 
But though the inner part of the lens of the Lamprey is harder than 
the external part, there is by no means so much difference in this 
