226 JOHN DENIS MACDONALD. 
primitively represented a mouth. It may perhaps have lost 
this function owing to an increase of food yolk in the ovum 
preventing its being possible for the blastopore to develop 
directly into a mouth, and necessitating the formation of a 
fresh mouth. If such were the case, there would be no reason 
why the blastopore should ever again serve functionally as 
a mouth in the descendants of the animal which developed 
this fresh mouth. 
On the Anatomy of the BorpER of the Postrrtor Evastic 
Lamina of the Cornua, in relation to the Fisprous 
TissuE of the LigAmMentuM Ixtpis Precrinatum. By 
JoHn Denis Macponatp, M.D.,F.R.S., Deputy-Inspector 
General, R.N.; Assistant-Professor of Naval Hygiene, 
Army Medical School, Netley. (With Plate XI.) 
On dissecting the human eye with the view of demon- 
strating the generally admitted metamorphosis of the whole 
border of the posterior elastic lamina of the cornea into 
the fibrous tissue from which the little tendons of the liga- 
mentum iridis pectinatum arise, 1 was surprised to find that 
no such transformation was anywhere to be detected. The 
two structures, though, indeed, associated in a very intimate 
and peculiar manner, were nevertheless, perfectly distinct 
and not to be confounded with one another. This discovery 
led me to examine the eye of the sheep more minutely in 
reference to the point in question, as the pillars of the iris 
in that animal are very distinctly marked, being much less 
crowded than they are even in the ox. The result of the in- 
vestigation may be simply stated as follows : 
The peripheral tendon-like processes of the pectinated 
ligament (Fig. 1 and 2 c) were observed to perforate the 
border, divide dichotomously (e), intercommunicate (f), and 
break up, on its anterior surface, into a beautiful fibrous 
plexus (g) with a disposition of its elements ina concentric 
rather than in a radial direction. 
Moreover, the little tendons, on entering the lamina, were 
enveloped by conical extensions of structureless substance 
(d), more strikingly resembling a coating of vitreous 
enamel than the tubular reflections of a membrane as ordi- 
narily understood. I have taken the following extract from 
Kolliker’s ‘ Microscopic Anatomy’ (p. 541), as affording a good 
statement of the present acceptation of the structure of the 
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