374 THE ORIGIN OF VERTEBRATES 
he describes them simply as conical eminences, and states that they 
“yecouvrent un pore analogue a celui des poils mais plus petit; 
il est rempli par le protoplasma de la couche hypodermique.” 
From the ganglion, according to him, nervous prolongations pass, 
which traverse the chitinogenous layer and terminate at the base 
of the conical eminences. Each of these prolongations “ présente 
sur son trajet, mais un peu plus prés du ganglion que de sa termi- 
naison périphérique, une cellule nerveuse fusiforme (g.) offrant, 
comme celles du ganglion, un gros noyau.” He illustrates his 
description with the following, Fig. 153, 
taken from his paper. 
I have not been able to obtain any evi- 
dence of a fusiform nerve-cell on the course 
of the terminal nerve-fibres as depicted by 
him ; fusiform cells there are in plenty, as 
depicted in my drawing, but none with a 
large nucleus resembling those of the main 
ganglion, In no case, either in the flabellum 
or in the branchial organs of Limulus, or in 
the pecten-organs, have I ever seen a ganglion- 
cell within the chitin-layer; all the nuclei 
seen there resemble those of the cells of 
the hypodermis or else the elongated nuclei 
characteristic of the presence of nerve-fibres. 
Gaubert’s drawing is a striking one, and I 
Fic. 153 (from GavuBERT). E 
Section or a Toorn have looked through my specimens to see 
or PecrenorScorrron. whether there was anything similar, but have 
n., nerve; gl., ganglion. —_ hitherto failed to obtain any definite evidence 
of anything of the kind. 
I feel, myself, that an exhaustive examination of the structure 
and function of the pecten of scorpions ought to be undertaken. At 
present I can only draw the attention of my readers to the similarity 
of the arrangement of parts, and of the nature of the end-organs, in 
the sense-organs of the flabellum of Limulus and of the pecten of 
the scorpion. In both cases the special nerve-fibres terminate in 
a massive ganglion, situated just below the chitinogenous layer. In 
both cases the terminal fibres from these ganglion-cells pass through 
the modified chitinous layer to supply end-organs of a striking cha- 
racter; and although the end-organ of the pecten of the scorpion does 
“i 
‘it 
