The Eye of Peripatus. 
By 
William J. Dakin, D.Se., F.L.S., F.Z.S., 
Derby Professor of Zoology, University of Liverpool ; 
late Professor of Biology in the University of Western Australia. 
With Plate 7 and 3 Text-figures. 
Tue first description of the minute structure of the Eye 
of Peripatus was given by Balfour (1) in his memorable 
paper on the anatomy of Peripatus capensis. So far 
as I am aware nothing has been added to our knowledge of 
the structure since that date, despite the advances in micro- 
seopical technique, and the rather thorough investigation 
of invertebrate visual organs. Other arthropod eyes have 
received considerable attention, and this seems strange at 
first because a comparison of the Peripatus eye with that 
of other arthropods should be highly interesting by reason of 
the phyletic position occupied by the Onychophora. 
The development of the eye was followed by Sedgwick (4), 
but nothing was added to the previous knowledge of the 
structure of the adult eye, although the origin of the different 
parts was very clearly shown. 
In Balfour’s illustration, the structure of the eye of Pe ri- 
patus capensis is shown in longitudinal section through 
the head. This figure has been often recopied, and it will 
be well to take note of the details brought out (see Text-fig. 1, 
which is a copy of that after Balfour in this Journal, 
vol. 23). The general cuticle of the body wall is continued 
as a thin layer over the eye. Below this is the cornea—a layer 
of epithelial cells, which are continuous with the epidermis. 
Between the cornea and the lens there is another cell layer 
which appears to terminate peripherally against the region 
marked pigment. There is no evidence to show that the 
structures masked by the pigment were ever brought to light. 
NO. 258 N 
