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Proceedings of the Royal Society of Edinburgh. [Sess. 
(which also appear to form a covering for the maxillary excretory gland) 
with other ventral endoskeletal structures are described in detail. All 
are rigidly fixed to the maxillo-sternal framework, which is capable of 
independent movement. 
7. The Alimentary Canal. — The foregut of Glyptonotus is not a gastric 
mill; the muscle-provided involutions of its wall (exactly analogous to 
those in Bathynomus ) are concerned simply with onward propulsion of 
the food, i.e. with swallowing. Between the midgut and the hindgut, the 
two opposed ends of which are not in exact alignment, is a strongly con- 
tractile part of the gut, which acts as a sphincter. The hepatic caeca could 
not be examined. Glyptonotus is carnivorous. 
8. The Eyes and the Chromatophore- System. —By experiment on colour 
change of Idotea it has been shown that the eye of this animal acts as a 
double mechanism, the ventral half being functionally separable from the 
dorsal. Glyptonotus has retractile chromatophores, and probably under- 
goes colour change in accordance with different modes of eye illumination. 
Its eye is divided into two entirely separate parts, one lying on the dorsal 
the other on the ventral aspect of the cephalon. 
The cost of providing the illustrations which accompany this paper was 
defrayed by a grant from the Earl of Moray Endowment for the promotion 
of research in the University of Edinburgh ; and the expense of preparing 
the blocks was defrayed by a grant from the Carnegie Trust. 
I have to record my thanks to Dr W. S. Bruce, not only for the 
material provided, but for information relating to the quarters inhabited 
by Glyptonotus. 
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