PRESENCE OE EYES IN SHELLS OF CERTAIN CHITONIDjE. 43 
directly to their source, but it is probable that they proceed 
from the parietal (branchial) nerves. When sections cut 
vertically through the decalcified tegmentum, so as to include 
the adjacent articulamentum and girdle, the whole shell and 
its attachments in situ are examined, I find abundance of 
fibrous structures passing from the girdle tissues directly to 
join the plexus of tissue in the tegmentum. These series of 
fibres are definitely arranged and readily stained, are of deep 
origin, and cannot be regarded as mere processes of the mantle. 
I have, however, been unable to trace them to any definite 
source amongst the muscular tissues. Similar fibres enter the 
tegmenta on their under sides abundantly along their sutural 
lines. I believe that nerves must accompany these fibres or 
form part of them. Haller describes a series of mantle nerves 
as given off from the branchio-visceral cords between every 
two gills. Each nerve turns outwards towards the mantle 
border. He was unable to determine whether it also gives 
off fibres which proceed inwards, and supply the body wall 
beneath the shells . 1 The nerve-fibres are not to be distin- 
guished in the main stems of the ramifications from the tissue 
with which they are bound up, but within the eye capsules 
the optic nerves break up into bundles of fine fibres which 
supply the retina and must be nervous in nature. 
Megalsesthetes and Micrsesthetes. 
Erom the ramifications of soft tissue are given off branches 
to each of the megalopore canals ; these follow the curved 
course of the latter and expand within the megalopores into 
the “ papilliform bodies” of Van Bemmelen, to which I shall 
apply the name megalsesthetes, believing that they are peculiar 
organs of touch and are at all events peculiar to Chitonidse and 
essentially different in structure and origin to the spines borne by 
the girdle in that group. They require a special designation. 
In some species the strands passing to the megalopores pass 
1 B. Haller, “ Die Organisation der Chitonen der Adria,” ‘ Arbeiten aus 
dem Zool. Inst, der Universitat Wien,’ T. iv, 3 Heft, 1882, S. 10. 
