OCCUPATION OF A TABLE AT THE ZOOLOGICAL STATION AT NAPLES. 198 
conjunction with Plankton and Hydrographic Research, and for that 
reason the report is rather incomplete as regards final results. I hope 
to have complete papers published by the end of this year, in which 
due acknowledgment to the British Association will be made, and copies 
will be handed to the Committee. I feel it my duty to thank the British 
Association for the opportunity of working at Naples, and must also 
mention the kind way in which the various members of the staff of the 
Zoological Station gave every possible help. The researches dealt in 
general with the histology and physiology of the nervous system and 
sense organs of lamellibranchs, continuing my previous work on Pecten. 
Though forty-four years have elapsed since the first detailed work on 
the eye of Pecten, it still remains incompletely known, owing to the 
extreme technical difficulties. I intended, therefore, to make a fresh 
and complete comparative study of the structure of the Pecten eye, using 
the new methods which have elucidated so many points in the structure 
of invertebrate sense organs in the last few years. 
Another branch was the study of the visceral ganglion and the inner- 
vation of the osphradium. The former is particularly interesting in 
Pecten, and unique as regards complexity in the Lamellibranchiata. I 
hoped to trace the distribution of the nerves in the ganglion in order 
to make out whether definite regions were concerned with the innerva- 
tion of separate organs, and finally to consider in detail the histology. 
With regard to the eye, it would be impossible here to discuss at all 
fully the histological structure without figures, but the following points 
may be noted. Hesse was able to see a layer of fibres lying between the 
cornea and lens, and bases a theory of accommodation on their presence 
(they stain, according to him, as muscle fibres), together with a peculiar 
structure in the lens cells. I find no trace of accommodation in the 
Pecten eye, and histological evidence points to these fibres being of 
connective tissue. I have been able to find between the cornea and lens 
numerous connective tissue cells which are produced into the extremely 
long fibres seen by Hesse. 
Certain points remain to be added to the known structure and shape 
of the lens cells. The axial fibril of the rod is with certainty a con- 
tinuation of a fibril in the rod cell. It is thicker in the former, and 
often remains in macerated specimens when the rest of the rod has been 
disintegrated. 
There is a growing region for rod cells and rods round the periphery 
of the retina, and the axial fibril is always far more distinct in the young 
cells than in those from the middle of the retina. There are large and 
small eyes often in close proximity on the same valve; the difference 
between these is simply the number of the elements-——-small eyes have 
fewer rod cells and rods. In most ways the axial fibril does not display 
the characters of a neurofibril, and may possess simply a supporting 
function. Numerous delicate supporting fibrille run longitudinally 
down the rod cells arranged at the periphery. The eyes are innervated 
directly from the visceral ganglion. 
The visceral ganglion consists of two central prominent lobes, with 
one or two smaller ones at their sides, a lobe partially covering the two 
first mentioned, and two large lateral crescentic lobes. I have made 
out the roots of the various nerves in detail. The branchial nerve arises 
by two roots. A separate nerve arising from the upper side (the sur- 
face against the adductor being considered the lower) innervates the 
1909. Oo 
